阅读理解。 Do I really need a helmet just to ride to class? First, ask your physics professor what can happen to a head dropped from the normal height where you ride, say about 5 feet up, when it hits the walkway? He will tell you about the forces the head can experience from that drop height. Bike helmets are tested in a two-meter drop, a little higher, but that five feet is all the force you need to mess up your brain. You don't need forward speed at all, although it can make it worse. Then think about accidents that happen when you ride on campus. Have you had near-collisions (碰撞) or actual collisions with pedestrians as the students change class? Do you ever hurry to get to class and take little chances? Have you ever seen a patch of ice or sand on a campus sidewalk? We would bet that you know more risk factors than we do. And what do the statistics say? There are 800 people killed on bikes, and a half million, more or less injured, in the US every year. Nobody keeps track of how many of those were on a campus. But we do know that you are making a major investment in yourself for a lifetime of good returns. People with head injuries can remember how much more they were able to do mentally before the crash, and that hurts long after other parts heal (愈合). The effects can last forever. At your age you are just beginning to realize how much pleasure in life comes from being experienced, smart and educated. You don't want to take a chance with that. It means a lot to you. Helmets are cheap at Wal-Mart or Target, and the cheap ones work fine if you fit them carefully. It really won't mess up your hair much in a short ride. Give it a try. 1. The aim of this text is probably______. A. to introduce a way to protect one's head B. to remind students to wear helmets while riding C. to persuade students to buy more helmets at Wal-Mart D. to warn students against bicycle riding because of danger 2. Helmets are necessary for bicycle riders on campus because _____. A. they will meet with an accident sooner or later B. the brain will be protected during an accident C. their hair will not be messed up in a short ride D. they will have to fight against the students from other classes 3. In paragraph three, the writer mainly wants to tell us that _____. A. riding bicycles is too dangerous B. the traffic on the campus is often out of order C. the number of bicycles on campus should be limited D. it is difficult to avoid accidents while riding bicycles on campus 4. The 'major investment' refers to the money for _____. A. a safer bike B. bike accidents C. a helmet D. a campus insurance 5. This passage would probably appear in the part of ______ on a website. A. Science B. News C. Education D. gym