题目内容：

Are you carrying too much on your back at school? You’re not alone. 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 schoolbags. “It hurts my back when I run,” said Oberlin Reyes, a student in Virginia. ”It’s hard to get up the stairs with my schoolbag, because it’s too heavy. ”They had common schoolbags with two straps  (带子) to carry them, but a number of students with heavy books use a special bag which have wheels and can roll on the ground.

Shirley Park, whose schoolbag weighed 10 kilograms, said she changed to rolling one 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 schoolbag; less homework.

Here are Doctors’ suggestions:

①Lighten the schoolbag. Clean out binders(活页材料)and take home only the books you need that night.

②Wide 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.

③Pack smart. The heavier things should be packed closed to the back.

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

1.What is the main idea of the passage?

A. The problem of student’s school life.

B. The problem made by too much homework

C. What is the best backpack for a student

D. How to make students’ schoolbag light.

2.According to the underlined sentence, from a few students’ suggestion, we know        .

A. students have to do too much homework

B. The more books in the schoolbag, the better.

C. Schoolbags without wheels are bad for students.

D. too much homework leaves students no free time.

3.According to the passage, it’s better for a student of 40 kilograms to carry a bag of       

at most by the words of experts.

A. 10kg    B. 8kg    C. 6kg    D. 7kg

4.If students follow the doctor’s suggestions, they        .

A. will have fewer books but learn better    B. can learn how to help themselves

C. may feel their schoolbags are lighter    D. will know how to wear backpacks.