. Are you carrying too much on your back to school? Lots of kids of your age are. Not only are students in China suffering from the problem, but kids in the United States are puzzled by heavy school bags. Experts are starting to worry that young students are having back and neck problems as a result of school bags being too heavy for them. It is hard for me to get up the stairs with my bag because it's so heavy, said Rick Hammond, an 11-year-old student in the US. Rick is among the students who have regular backpacks(背包) with two straps (带子) to carry them, but a number of other students choose rolling backpacks. But even with rolling backpacks, getting up stairs and buses with them is still a problem for kids. Many of them have hurt their knees, backs or necks because of heavy school bags. But how much is too much? Experts say students should carry no more than 10 to 15 percent of their own body weight. Scott Bautch, a Wisconsin back doctor, said kids under 4th grade should stay with 10 percent, but it’s also important that older kids don’t go beyond (超出) 15 percent, because their bones are still growing. Bautch explained that there are other injuries caused by backpacks. Kids are losing their balance and falling down with these backpacks, he said. Parents and teachers are starting to tell kids to only take home library books they will be reading in the evening. Some teachers are using worksheets (作业单 ) or thin workbooks for students to take home. One of the best answers is, as some kids suggest, to have no homework at all! 60. According to experts, a primary student in Grade 6, who is 4 0 kilograms, should carry a bag   weighing ______ kilograms at most. A. 4 　     B.6      　C.8 　    D.10 61. As school bags are too heavy for younger students to carry, they ______. A. show no interest in studying at s chool. B. often fall ill C. are having back and neck problems D. usually ask their parents for help 62. The author wrote the passage to _____. A. seek(寻找) ways to solve the problem of heavy bags B. appeal (呼吁) to teachers for caring for the students C. criticize(批评) the government for having done nothing to help students D. tell us that heavy bags are bad for students’ health 63. Parents and teachers are starting to tell kids to take home only library books they will be   reading in the evening to ______. A. make students more interested in reading than watching TV B. give them more free time to play C. make their bags easier to carry D. let them sleep early at night