题目

已知点O在二面角α－AB－β的棱上，点P在α内，且∠POB＝45°．若对于β内异于O的任意一点Q，都有∠POQ≥45°，则二面角α－AB－β的大小是_________． 答案：90°阅读理解     Every culture has a recognized point when a child becomes an adult, when rules must be followed and tests passed.     In China, although teenagers can get their ID cards at 16, many only see themselves as an adult when they are 18. In the US, where everyone drives, the main step to the freedom of adult life is learning to drive. At 16, American teens take their driving test. When they have their license, they driveinto the grownup world.     "Nobody wants to ride the cheese bus to school, " said Eleanor Fulham, 17. She brought thepressure back to memory, especially for kids from wealthier families. "It's like you're not cool if youdon't have a car, " she said.     According to recent research, 41% of 16 to 19yearolds in the US own cars, up from 23% in 1985. Although, most of these cars are bought by parents, some teens get parttime jobs to help pay.     Not all families can afford cars for their children. In cities with subways and limited parking, someteenagers don't want them. But in rich suburban areas without subways, and where bicycles are more for fun than transportation, it is strange for a teenager not to have a car.     But police say 16yearolds have almost three times more accidents than 18 to 19yearolds. This has made many parents pause before letting their kids drive.     Julie Sussman, of Virginia, decided that her son Chad, 15, will wait until he is 17 to apply for hislearner's permit.     Chad said he has accepted his parents' decision, although it has caused some teasing from his friends.  "They say that I am unlucky, " he said, "But I'd rather be alive than driving, and I_don't_really_trust_my_friends_on_the_road,_either."     In China as more families get cars, more 18yearolds learn to drive. Will this become a big step tobecoming an adult?1. Which may serve as the best title of the article?A. Cars Helping You to GrowUpB. Driving into the GrownUp WorldC. Teenagers' Driving in AmericaD. Recognized Point of Becoming an Adult2. 16yearold drivers have more accidents possibly because________.A. they want to show themselves offB. they are never experienced driversC. older people always drive betterD. they never drive carefully on the road3. Which may NOT be taken into consideration when deciding whether to buy a car?A. How well off the family is.B. Whether the kid is old enough.C. What traffic condition there is around.D. Whether it's practically needed.4. When Chad said "I don't really trust my friends…he meant that________.A. he might run into his friends if he drove B. he didn't agree with his friendsC. he might not be safe if his friends droveD. he was afraid that his friends might well lie to him5. The passage mainly gives information about ________.A. an American cultureB. a cultural difference between America and ChinaC. a change in the Chinese cultureD. the relationship between driving and a person's development