1972年，作为中国问题观察家的费正清跟随美国总统尼克松访问中国。费正清当时谈到中美两国间的关系时说：“从1950年到1971年，华盛顿送上月球的人比派往中国的还多。”造成这种现象的主要原因是

函数$f\left(x\right)=x^{\frac{1}{2}}-(\frac{1}{2}{)}^x$的零点个数为(     )

 “关爱社会，学作负责任的公民”是当代中学生在成长中应当养成的品德。
【同学行动】八年级（3）班的班委们相约周六去养老院看望老人们。但劳动委员小辉却因为临时改变主意决定参加好朋友的生日会不能来了。班长只好带着其他班委到养老院去打扫卫生和表演节目。班长在打扫卫生时把养老院里的水瓶打破了，虽然没有人看见，但他还是主动承认并作出赔偿。
【学校调查】某中学准备开展一些公益活动，在此之前，学校对学生参加公益活动情况进行了一次抽样调查。下表是调查统计的结果：

    One day, several young people went for a picnic. They walked in the open air with 1.

    As soon as they came to a river, they 2 by the clear and calm water. They played with cool water excitedly. Suddenly, a lovely 3 passed by Tom. He tried to catch it, 4 the fish was just swimming a few feet ahead of him. He ran 5 it, hoping to catch it.

    Gradually, Tom came to the water with waist deep. He felt 6, so he wanted to jump out of the water. 7 up and down in the water, he went farther and farther away from the bank. Just at that time, Barry saw this, he offered 8 help to Tom at once. Tom saw someone 9 to him, he caught the person 10 was close to him. Unfortunately, Barry was dragged into the water. The two struggled in the water 11.  Amy, on the bank, noticed that, and she 12 others near the bank.

    Hearing their cries, two farmers near the river took a long rope there. They threw one end of the rope to 13 of them in the water. Together, all the people on the bank pulled 14 end.

    Finally, the two boys were saved!

    The experience has told us 15 we should do something to help others correctly.