摘要：John will the medicine when it is left after Dec.1st, 2002. A. throw away B. stop to take C. take once D. take six times more Passage 72 Passage 73 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 . “It hurts my back when I run, said Oberlin Reyes, a student in Virginia. “It’s hard to get up the stairs with my backpack, because it’s too heavy. Oberlin is among students whose backpacks were weighed for a week in a recent study. They had regular backpacks with two straps 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 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 . 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 pick up the pack, and don’t just bend over at the waist (腰).