---Will you go with us for an outing on Saturday?
--- I’d like to, but I am really busy these days. I can’t _______ a whole weekend.

You are probably familiar with the saying：An apple a day keeps the doctor away. A recent research carried out by the Chinese University of Hong Kong may change the saying:
An apple a day may keep aging away.
The research chose fruit flies(果蝇), as they share many genes(基因)with humans. The fruit flies were either fed normally or had an apple extract(浓缩物) added to their diet.
It turned out that those fruit flies that were given apple extract lived about 55 days—five days longer than the flies that were normally fed. The research group also found it easier for the flies to walk，climb and move about as they aged.
According to the result, the researchers believed that the antioxidants(抗氧化剂) in the apple extract helped clean up dangerous chemicals(化学物质) that cause illnesses，as well as aging.
In another study，researchers examined diets of thousands of women. They discovered that those who regularly ate apples were 20 percent less likely to suffer heart illnesses and stroke.
The apples’ genetic code(遗传密码) was discovered recently. It allows scientists to develop nicer and healthier fruits. Researchers are already using the information to grow a kind of apples full of antioxidants that can keep eyes and joints healthy and protect humans against heart illnesses and cancer.
Apples that kill the desire(欲望) to eat could also be produced, with the first“extra-healthy’’apples on supermarket shelves within just four or five years.
The team that keeps studying apple DNA includes 100 scientists from five countries. Their research also suggests that around 65 million years ago, when dinosaurs began to die off the plant，which would finally become today’s apple tree, experienced a great genetic change. The number of many of its genes doubled. The extra genes allowed the apple to get used to worse conditions and go through a different development from peaches，strawberries and other related fruits.
【小题1】Why were fruit flies used for the research?

A．Apples produce chemicals that can change human genes.

B．Apples have antioxidants that kill chemicals that cause aging.

C．Apples are rich in vitamins that are needed in humans’bodies.

D．Apples produce chemicals that make apples taste more delicious.

You might have noticed that the cost of food has gone up.In fact the price of wheat and rice has nearly doubled in the past few years.It’s thought that right now，850 million people—that’s more than 10 times the population of the UK—are short of food because it’s too expensive or there’s not enough of it.
The price of basic food such as wheat and corn has stayed the same for quite a long time，about 30 years.But as the world’s population is getting bigger，there’s more pressure to feed more people，plus there’s less land and water to go round.
Another reason is climate（气候）change.Droughts and floods make it hard to grow crops like rice and grain.The price of oil has gone up and that makes it more expensive for farmers to run their tractors and to transport the food they make.And lots of fields are being used to grow crops to make other things that can’t be eaten—which is bad news for hungry people.
The main losers are poor people who live in cities in poor countries，who are facing higher prices for food.Some people are doing well out of the food crisis（危机） though.Farmers in rich countries like the US，Canada and Australia are getting record prices for their harvests.
World leaders are meeting in the Italian capital Rome to talk about the problem of rising food prices.Some countries are helping out with the cost of foods and international aid agencies have called for more money for food production in poor countries.
【小题1】The price of food goes up because all of the following EXCEPT _____.