-----Are these  your brother’s books?
------ Yes, ______are.
A this           B that          C these           D they

Are you carrying too much on your back at school? I’m sure lots of children of your age will, say "Yes". Not only the students in China have this problem, but children in the United States also have heavy school bags.
Doctors are starting to worry that younger and younger students are having back and neck problems as a result of schools bags being too heavy for them.
"It’s hard for me to go upstairs with my bag because it’s so heavy, "said Rick Hammond, an 11-year-old student in the US.
Rick is among students who have common school bags with two straps(带子) to carry them, but many other students choose rolling(有滚轮的)bags.
But even with rolling bags, getting up stairs and buses is still a problem for children. Many of them have hurt their backs and necks because of the heavy school bags.
But how much is too much? Doctors say students should carry no more than 10% to 15% of their own body weight(重量).
Scott Bautch, a back doctor, said children under Grade 4 should stay with 10 % . But it is also important that older children don’t stay with over 15 %, because their bodies are still growing. "Children are losing their balance(平衡) and falling down with their school bags, "he said.
Parents and teachers are starting to tell children to only take home library books they will be reading that night. Some teachers are using pieces of paper or thin workbooks for students to take home.
One of the best answers is, as some children said, to have no homework at all!
【小题1】 From the passage we can know that      .

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