The bicycle is one of the simplest yet most useful inventions in the world. What is most surprising is that it was not ___1__ earlier, although the great inventor Leonardo Da Vinci had drawn pictures for bicycles and also for flying machines and some other things. Those things were not produced___2___ long after he died.

　　A person riding a bicycle uses ___3___ energy to make the bicycle move, and there is no pollution at all when you are riding. Even so, in developed ____4___, most people don’t travel to work by bicycle. It is not because the bicycles are expensive or people feel___5____ if they ride to work. It’s because __6___ cars on the roads becomes larger. It certainly becomes ___7___ to ride a bicycle. As a result, more people put their bicycles away and go to work ___8___ their cars cars, and in this way, the situation is made more serious.___9___ the best way to make riding safer and more popular is to create paths (开设通道) only for bicycles, and to make ___10___ so difficult and expensive for drivers to take their cars into the city that they will go back to use their bicycles.

The bicycle is one of the simplest yet most useful inventions in the world. What is most surprising is that it was not ___1__ earlier, although the great inventor Leonardo Da Vinci had drawn pictures for bicycles and also for flying machines and some other things. Those things were not produced___2___ long after he died.
　　A person riding a bicycle uses ___3___ energy to make the bicycle move, and there is no pollution at all when you are riding. Even so, in developed ____4___, most people don’t travel to work by bicycle. It is not because the bicycles are expensive or people feel___5____ if they ride to work. It’s because __6___ cars on the roads becomes larger. It certainly becomes ___7___ to ride a bicycle. As a result, more people put their bicycles away and go to work ___8___ their cars , and in this way, the situation is made more serious.___9___ the best way to make riding safer and more popular is to create paths (开设通道) only for bicycles, and to make ___10___ so difficult and expensive for drivers to take their cars into the city that they will go back to use their bicycles.

Most people want to work, but in today’s word ,it is more difficult to find work for everybody.The economics of the world need to grow by 4% each year just to keep the old number of jobs for people.
Often this is not possible,and so more people are out of work.
Some people have no jobs now because new machines can do the work of many people do in a short time.Also, machines do not ask for more money and longer holidays. In all the countries of the world, machines are taking work from people ,not only in factories but also on the farms.
One machine can often do the work of forty people. About 75,000 people are moving to the cities a day to look for jobs ,but only 70% of them can find jobs .
【小题1】The economics of the world need to grow to______.

The human body is a living machine, and, like all machines, it needs “fuel” to supply it with energy. This is provided by the food we eat. But how much do we need to stay healthy?
The energy value of food is usually measured in calories(卡). A calorie is the amount of heat required to raise the temperature of 1 kg of water by 1℃. The number of calories people need per day is different, as the picture shows. Also, the number of calories you use at any one moment normally depends on the activity you are in. For example, you need more calories for standing than for sitting, more for running than for walking, and so on.
The energy in food is in the form of three kinds of chemical materials—carbohydrate（碳水化合物）, protein（蛋白质） and fat. Carbohydrate provides 3.8 Cal /gm of the energy, protein 4.0 Cal/gm, and fat 8.8 Cal/gm. Each food contains different amounts of these materials, as the round pictures show.
(P= protein      C= carbohydrate    F=fat)
【小题1】How many calories are needed to raise the temperature of 5kg of water from 35℃ to 90℃?