一口井水，水面比井口低3m，一只蜗牛从水面沿着井壁往井口爬，第_爱下问搜题

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问题解答题

一口井水，水面比井口低3m，一只蜗牛从水面沿着井壁往井口爬，第一次往上爬了0.5m后又往下滑了0.1m；第二次往上爬了0.42m，却又下滑了0.15m；第三次往上爬了0.7m，却又下滑了0.15m；第四次往上爬了0.75m，却下滑了0.1m第五次往上爬了0.55m，没有下滑；第六次蜗牛又往上爬了0.48m，问蜗牛有没有爬出井口？

答案

由题意得，蜗牛往上爬的高度为：0.5+（-0.1）+0.42+（-0.15）+0.7+（-0.15）+0.75+（-0.1）+0.55+0.48=2.90＜3，

故没有爬出井口．

完形填空

完形填空先通读下面的短文，掌握其大意，然后在所给选项中，选出最佳选项。
At the beginning of this century, medical scientists made an interesting discovery: we are built not just of flesh (肌肉) and blood but also of time. They were able to show that we all have a ‘body clock’   1  us, which controls the   2  and fall of our body energies. It can   3  us different from one day to the next.
The idea of a ‘body clock’ should not be too   4  because the lives of most living things are controlled by the 24-hour night-and-day cycle (循环). We feel   5  and fall asleep at night. We become   6  and energetic during the day. Most people will have a bad feeling if the 24-hour cycle is   7 . For example, people who are not used to working at night can find that lack (缺少) of sleep causes them to 8  badly at work.
9  the daily cycle of sleeping and waking, we also have other cycle which lasts longer than one day. Most of us would   10 that we feel good on some days and not so good on others; sometimes our ideas seem to be so active and at other times, they are not.

D．frightening

C．comfortable

D．Rather than

单项选择题

关于支原体肺炎，以下哪项是错误的

A．秋季发病多
B．儿童青少年多
C．可引起肺炎性浸润和空洞形成
D．有咽炎，支气管炎表现
E．半数病例无症状