—__________are you in?　　　

—I'm in Class Four.

[　　]

A. What number　　    　B. What grade

C. What class　　　　 　D. What row

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.

Are you carrying too much on your back at school? You’re not alone. Back experts in the United States are worried that young students are having back and neck problems as a result of carrying too much in their backpacks (schoolbags)
“It hurts my back when I run,”said Oberlin Reyes, a student in Virginia. “It’s hard to go up the stairs with my backpack,because it’s too heavy,”
Oberlin was among students whose backpacks were weighed for a week in a recent study.
They had regular backpacks with two straps(带子)to carry them, but a number of students with heavy loads had switched to rolling backpacks (which have wheels and can roll on the ground).
Shirley Park, whose backpack weighed 10 kilograms,said she changed to a rolling backpack because she was starting to have back  pain.
How much is too much?Experts say students should carry no more than 10 to 15 percent of their own body weight.
A few students had one suggestion to lighten the load:less homework.
P.S.( 附)Doctor’s suggestion:
1 Lighten the load. Clean out binders(活页材料)and take home only the books you need that night.
2 Wide straps are better. They send out the weight over your shoulders more evenly(均匀)。 And be sure to wear both straps rather than hanging the pack over one shoulder.
3. Pack smart. The heavier things should be packed closed to the back.
4.Bend both knees when you pich up the pack ,and don’t just bend over  at the waist.(腰)
【小题1】“_________”is the main idea of the text.
A The problem of backpacks is worth studying.
B The problem made by heavy backpacks
C What is the best backpack for a student.
D      How to make students’backpacks light.
【小题2】According to Oberlin Reyes and Shirley Park, we know________.
A students have to do too much homework
B students have to carry several backpacks
C backpacks without wheels are bad for students
D too much homework leaves students no free time
【小题3】The expression “switched to” in the text perhaps means________.
A started to use  B turned to  C caught up   D used for
【小题4】According to the passage ,it’s better for a student of 40 kilograms to carry a backpack of _____at most by the words of experts.
A 10kg    B 8kg  C 6kg    D 7kg
【小题5】 If students follow the doctor’s suggestions they ________.
A may lighten their backpacks
B can learn how to help themselves
C may feel their backpacks are lighter
D will know how to wear backpacks

Are you carrying too much on your back at school? You’re not alone. Back experts(专家) in the USA are worried about that young students are having back and neck problems because they are carrying too much in their backpacks .

“It hurts my back when I run,” said Ebelin Reyes, a student in Virginia. “It’s hard to get up the stairs with my backpack because it’s too heavy.” Students have to carry heavy backpacks on their backs for a whole week’s study. Ebelin is one of them. They have   regular(固定的)backpacks with two straps(带子) to carry them, but a number of students with heavy loads(负担) have switched to rolling backpacks. The backpacks have wheels and can roll on the ground. Shirley Park’s backpack weighs 10 kilos, and she said, “I’ll change to a rolling backpack because I am starting to have back pain.”

How much is too much? Experts say that students should carry no more than 10% to 15% of their own body weight. A few students have had a good idea to lighten(减轻) the load: less homework.

Doctor’s suggestions:

Lighten the load. Take home only the books the students need that day.

(2) Wide straps are better. They can send out weight over your shoulders (肩)and be sure to wear backpacks with two straps.

(3) The heaviest things should be packed closest to the back.

(4) Bend(弯曲) both knees when you pick up the pack, don’t just bend over the waist(腰).

1.The main idea of the passage is about _______.

A．the problems made by rolling backpacks

B．the advantage of backpacks

C．the best backpacks for students

D．how to lighten students’ backpacks

2.From what Ebelin Reyes and Shirley Park said, we know______.

A．students like to carry heavy backpacks

B．students have to do a lot of homework

C．backpacks with wheels are bad for students

D．students have no time to play because of heavy backpacks

3.The underlined word “switch to” means______.

A．use for           B．turn to            C．catch up          D．begin to use

4.According to the experts, it’s better for a student of 40 kilos to carry a backpack of ____ at most.

A．10 kilos           B．8 kilos            C．6 kilos            D．7 kilos

5.If students follow the doctor’s suggestions, they______.

A．may do less homework

B．may feel their backpacks are lighter

C．can learn how to enjoy themselves

D．will know why to wear heavy backpacks