（B）

It is natural that children are curious about the world around them. For example, they want to know how their hearts beat. They want to know why the ocean water tastes salty.

As children grow up, they become curious about different kinds of things. When they are babies, they are interested in the parts of their bodies and in the smiles of their mothers. Then they become interested in the physical world around them: the plants, the animals, and the sky. Later, they become interested in the things that people have made: wheels, bicycles, cars. And when they are adults, their curiosity continues. Sometimes this curiosity leads to a career in science.

       Scientists spend their lives trying to find out about the world. Those who work with the earth sciences study the earth, the oceans, and the skies. Other scientists who study living things work with the biological sciences. A third group of scientists study the physical sciences, e.g., physics, chemistry.

       These scientists have already discovered a lot about our world. For example, they tell us why your heart beats fast when you run. They say that when you are quiet, your heart normally beats sixty-five or seventy-five times a minute. Your heart is like a pump that pumps blood to all parts of the body. The blood carries oxygen and nutrition. When you run, your muscles work very hard and use the nutrition that the blood carries to them. The muscles need oxygen, too. So your brain sends a signal to the heart. The signal means that the muscles need more nutrition and oxygen. Then the heart beats fast and sends blood quickly to the muscles. It may beat 90 to 140 times a minute.

       Of course, scientists cannot answer all of our questions. If we ask “Why does the ocean water taste salty?” scientists will say that the salt comes from rocks. When a rock gets very hot or very cold, it cracks. Rain falls into cracks. The rain then carries the salt into the earth and into the rivers. The rivers carry the salt into the ocean. But then we ask, “What happens to the salt in the ocean? The ocean does not get saltier every year.” Scientists are not sure about the answer to this question.

       We know a lot about our world, but there are still many answers that we do not have, and we are curious.

46. Which of the following statements is true?

A. People are curious in the same way.

B. People in different countries are interested in different things.

C. Men and women are curious about different things.

D. People of different ages are interested in different things.

47. Scientists who work with the biological sciences study ______________________.

A. the earth, the oceans and the sky                           B. ocean water

C. plants and animals                                               D. man-made things

48. When you run, your muscles need ______________________________.

A. more nutrition and oxygen                                   B. more signals     

C. more salt                                                            D. water

49. A rock cracks ________________________________________.

A. in wet regions                                              B. in dry regions

C. at very high or very low temperatures     D. when salty water falls in

50. People are always curious because _________________________.

A. they cannot explain many things                    B. they know nothing about the world

C. they know little about the world                    D. they want to be scientists

How would you like to brush a crocodile’s teeth? Or give a shark a bath? Cats are well-known for the way they keep themselves clean by licking （舔）, but other animals have their own ways to stay clean as well. And tidiness can be important for their survival. Even cockroaches （蟑螂） have to keep their feelers clean to help them into food.

Many animals in the wild, such as deer, wolves and bears, have an automatic cleaning system. Insects like to attach themselves to animals to feed on the skin or blood. These parasites （寄生虫） can be unhealthy. But their “host” animals are constantly dropping skin and fur by a natural process. They also like to rub up against trees or rocks to comfort themselves, and this removes additional skin and fur. Along with old fur goes the dirt and parasites living in the fur. While these animals may sometimes take a bath when they enter or cross a river or lake, they don’t need the water to stay clean. They don’t get sweaty, because they don’t have sweat glands （汗腺） all over their bodies the way people do. Growing new skin and fur is enough to keep them clean.

Some animals and birds use dust to get clean. Chinchillas, a kind of small animal that lives in the mountains of South America, have a very fine fur. （They are raised for their fur, in fact.） If they took water baths, they might get too cold. So, instead, they roll around in fine dust, raising quite a cloud as they “bathe”. The dust helps to keep their fur and skin dry. This protects them from bacteria and parasites that enjoy warm and wet places. And the fine dust doesn’t stick in their fur for long. It falls off or blows away.

As for lions and tigers, their rough tongues act like combs and can remove dirt and loose fur. Why is it important for them to stay clean and smooth? It helps them stay cool in very hot summer or feel warm in cold winter.

64. What’s the main idea of this passage?

A. Animals enjoy living in a clean environment.

B. Animals fight against parasites in different ways.

C. Unlike people, animals hate staying in water.

D. For animals, cleanliness is a survival skill.

65. According to the passage, such animals as deer, wolves and bears clean themselves by        .

A. living with parasites

B. replacing their skin and fur naturally

C. climbing trees or rocks

D. having a bath in a river or lake

66. It can be inferred from the passage that the way some animals stay clean        .

A. is decided by their physical conditions

B. is better than the way people do

C. keeps them away from parasites all the time

D. helps them survive any danger in the wild

One warm day when I was walking in my backyard, I saw a pinecone(松球) on the ground. I picked it up, and some seeds fell out of it. Those seeds would be a tasty treat for a squirrel (松鼠).
I realized that pinecones were not always open like this one. Sometimes cones were tightly closed. I decided to find out why.
I gathered pinecones from my backyard. I watched them for over a year. Here’s what I learned.
Pinecones open and close slowly as the weather changes. When it’s cold or wet, cones are tightly closed. This protects the seeds inside from rain and snow.
When the weather becomes warm and dry, pinecones open. On a hot day, you might even hear the sound of cones popping open. The seeds inside may then fall to the ground. The wind may blow the seeds to places where they can grow into new pine trees. A seed has a better chance of taking root and growing when the weather is warm.
“Pine seeds are an important source of food for many animals,” says Monty Maldonado. He is a pinecone expert with the United States Forest Service. He says squirrels depend on pinecone seeds for most of their meals. They spend lots of time gathering and storing the cones. Maldonado says some animals eat only the seeds from a pinecone. But red squirrels and gray squirrels will eat the whole thing.
Small animals aren’t the only creatures that eat pine seeds. Maldonado says big grizzly bears (灰熊) and people eat them, too.
Seeds inside a pinecone are important for the growth of new trees and as food for animals. It is the pinecone’s job to protect them. So take note of the pinecones you see on the ground. They hold treasures inside.
45．According to the passage, when it is rainy, cones          .
A．are open   B．are usually shut       C．grow quickly    D．stop growing
46．According to Monty Maldonado,        .
A．not all squirrels eat the whole pinecone        
B．pine seeds are difficult to find for many animals
C．people in the forest are sometimes attacked by grizzly bears
D．most small animals depend on pinecone seeds for their meals
47．We can learn from the passage that on sunny days         .
A．seeds may fall out of the cones      
B．squirrels stay still in their nests      
C．it’s difficult for a seed to take root
D．the wind will put the pine trees in danger
48．In the last paragraph, the author points out that         .
A．more and more new trees need to be planted in future 
B．people should be responsible for protecting animals
C．people should be careful not to damage the pinecones  
D．squirrels now have few seeds to feed themselves
49．Which of the following is TRUE according to the passage?
A．The author learned why pinecones are not always open in the forest.  
B．The author gathered pinecones and observed them for a month.  
C．The author is fond of gathering and storing the cones. 
D．Pine trees are precious to animals and people.

One warm day when I was walking in my backyard, I saw a pinecone(松球) on the ground. I picked it up, and some seeds fell out of it. Those seeds would be a tasty treat for a squirrel (松鼠).

I realized that pinecones were not always open like this one. Sometimes cones were tightly closed. I decided to find out why.

I gathered pinecones from my backyard. I watched them for over a year. Here’s what I learned.

Pinecones open and close slowly as the weather changes. When it’s cold or wet, cones are tightly closed. This protects the seeds inside from rain and snow.

When the weather becomes warm and dry, pinecones open. On a hot day, you might even hear the sound of cones popping open. The seeds inside may then fall to the ground. The wind may blow the seeds to places where they can grow into new pine trees. A seed has a better chance of taking root and growing when the weather is warm.

“Pine seeds are an important source of food for many animals,” says Monty Maldonado. He is a pinecone expert with the United States Forest Service. He says squirrels depend on pinecone seeds for most of their meals. They spend lots of time gathering and storing the cones. Maldonado says some animals eat only the seeds from a pinecone. But red squirrels and gray squirrels will eat the whole thing.

Small animals aren’t the only creatures that eat pine seeds. Maldonado says big grizzly bears (灰熊) and people eat them, too.

Seeds inside a pinecone are important for the growth of new trees and as food for animals. It is the pinecone’s job to protect them. So take note of the pinecones you see on the ground. They hold treasures inside.

45．According to the passage, when it is rainy, cones          .

A．are open   B．are usually shut       C．grow quickly    D．stop growing

46．According to Monty Maldonado,        .

A．not all squirrels eat the whole pinecone        

B．pine seeds are difficult to find for many animals

C．people in the forest are sometimes attacked by grizzly bears

D．most small animals depend on pinecone seeds for their meals

47．We can learn from the passage that on sunny days         .

A．seeds may fall out of the cones      

B．squirrels stay still in their nests      

C．it’s difficult for a seed to take root

D．the wind will put the pine trees in danger

48．In the last paragraph, the author points out that         .

A．more and more new trees need to be planted in future 

B．people should be responsible for protecting animals

C．people should be careful not to damage the pinecones  

D．squirrels now have few seeds to feed themselves

49．Which of the following is TRUE according to the passage?

A．The author learned why pinecones are not always open in the forest.  

B．The author gathered pinecones and observed them for a month.  

C．The author is fond of gathering and storing the cones. 

D．Pine trees are precious to animals and people.

One warm day when I was walking in my backyard, I saw a pinecone(松球) on the ground. I picked it up, and some seeds fell out of it. Those seeds would be a tasty treat for a squirrel (松鼠).

I realized that pinecones were not always open like this one. Sometimes cones were tightly closed. I decided to find out why.

I gathered pinecones from my backyard. I watched them for over a year. Here’s what I learned.

Pinecones open and close slowly as the weather changes. When it’s cold or wet, cones are tightly closed. This protects the seeds inside from rain and snow.

When the weather becomes warm and dry, pinecones open. On a hot day, you might even hear the sound of cones popping open. The seeds inside may then fall to the ground. The wind may blow the seeds to places where they can grow into new pine trees. A seed has a better chance of taking root and growing when the weather is warm.

“Pine seeds are an important source of food for many animals,” says Monty Maldonado. He is a pinecone expert with the United States Forest Service. He says squirrels depend on pinecone seeds for most of their meals. They spend lots of time gathering and storing the cones. Maldonado says some animals eat only the seeds from a pinecone. But red squirrels and gray squirrels will eat the whole thing.

Small animals aren’t the only creatures that eat pine seeds. Maldonado says big grizzly bears (灰熊) and people eat them, too.

Seeds inside a pinecone are important for the growth of new trees and as food for animals. It is the pinecone’s job to protect them. So take note of the pinecones you see on the ground. They hold treasures inside.

45．According to the passage, when it is rainy, cones          .

       A．are open   B．are usually shut       C．grow quickly    D．stop growing

46．According to Monty Maldonado,        .

       A．not all squirrels eat the whole pinecone        

       B．pine seeds are difficult to find for many animals

       C．people in the forest are sometimes attacked by grizzly bears

       D．most small animals depend on pinecone seeds for their meals

47．We can learn from the passage that on sunny days         .

       A．seeds may fall out of the cones      

       B．squirrels stay still in their nests      

       C．it’s difficult for a seed to take root

       D．the wind will put the pine trees in danger

48．In the last paragraph, the author points out that         .

       A．more and more new trees need to be planted in future 

       B．people should be responsible for protecting animals

       C．people should be careful not to damage the pinecones  

       D．squirrels now have few seeds to feed themselves

49．Which of the following is TRUE according to the passage?

       A．The author learned why pinecones are not always open in the forest.  

       B．The author gathered pinecones and observed them for a month.  

       C．The author is fond of gathering and storing the cones. 

       D．Pine trees are precious to animals and people.