支持急性心包炎而不支持急性心肌梗死的诊断依据是（） A.硝酸甘油能缓解疼痛 B.早期

Every culture has a recognized (公认的) 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（证）, they drive into the grown-up world.

"Nobody wants to ride the cheese bus to school," said Eleanor Fulham, 17. "It's like you're not cool if you don't have a car," she said.

According to a recent research, 41% of 16 to 19 year olds in the US own cars, up from 23% in 1985. Although, most of these cars are bought by parents, some teens get part-time jobs to help pay.

Not all families can afford cars for their children. In cities with undergrounds and limited(有限的) parking, some teenagers don't want them. But in rich areas outside the city, if there are no undergrounds, and bicycles are more for fun than cars, it is strange for a teenager not to have a car.

But police say 16-year-olds have almost three times more accidents than 18 and 19-year-olds. This has made many parents stop before letting their kids drive. They need to wait until they are more experienced.

Julie Susiana, of Virginia, decided that her son Chad, 15, will wait until he is 17 to apply for his learner's permit (许可)

Chad said he has accepted his parents' decision, although it has caused some laughing 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 18-year-olds learn to drive. Will this become a big step to becoming an adult?

小题1:16-year-old drivers have more accidents possibly because _______.

A．they want to show themselves off

B．they are not experienced drivers

C．older people always drive better

D．they never drive carefully on the road小题2:Which may NOT be taken into consideration when deciding whether to buy a car?

A．How rich the family is.

B．Whether the kid is old enough.

C．What traffic condition there is around.

D．Whether it's practically needed.小题3:The passage mainly gives information about _______.

A．an American culture about teenagers' driving

B．a change in the Chinese culture

C．a cultural difference between America and China

D．the relationship between driving and a person's development小题4:Which may serve as the best title of the article?

A．Cars Helping You to Grow Up

B．Driving into the Grown-up World

C．Teenagers' Driving in America

D．Recognized Point of Becoming an Adult

（12分）如图所示，在粗糙水平台阶上放置一质量m=0.5kg的小物块，它与水平台阶间的动摩擦因数μ=0.5，与台阶边缘O点的距离s=5m。在台阶右侧固定一个1/4圆弧挡板，圆弧半径R=1m，圆弧的圆心也在O点。今以O点为原点建立平面直角坐标系xOy。现用F=5N的水平恒力拉动小物块，一段时间后撤去拉力，小物块最终水平抛出并击中挡板。（，取g=10m/s²）

（1）若小物块恰能击中挡板上的P点（OP与水平方向夹角为37°），求其离开O点时的速度大小；

（2）为使小物块击中挡板，求拉力F作用的最短时间。

精确新闻报道

世界文明的起源大概在？（）

A、公元前1500年

B、公元前1600年

C、公元前400年

D、公元前2000年