影响沉淀试验的因素包括（）。 A.抗原与抗体的比例 B.温度 C.盐浓度 D.以上3

Even though global warming may have made the weather more mild, many animals are still hibernating（冬眠）. It’s too bad that humans can’t hibernate. In fact we almost did.

Apparently, at times in the past, farmers in France liked a semi-state of human hibernation. So writes Graham Robb, a British scholar who has studied the sleeping habits of the French farmers. As soon as the weather turned cold, people all over the France shut themselves away and practiced the forgotten art of doing nothing at all for months.

In line with this, Jeff Warren, a producer at CBC Radio’s The Current, tells us that the way we sleep has changed since the invention of lighting.

When historians began studying texts of the Middle Ages, they noticed something referred to as “first sleep”, which was not clarified, though. Now scientists are telling us our ancestors most likely slept in separate periods. The business of eight hours’ continuous sleep is a modern invention.

In the past, without the artificial light, humans went to sleep when it became dark and then woke themselves up around midnight. The late night period was known as “The Watch”. It was when people actually kept watch against wild animals, although many of them simply moved around or visited family and neighbors.

According to some sleep researchers, a short of insomnia（失眠）at midnight is not a disorder. It is normal. Humans can experience another state of consciousness（清醒状态）around their sleeping, which happens in the brief period before we fall asleep or wake ourselves in the morning. This period can be a creative time for some people.

Playing with your sleep rhythms（节奏）can be dangerous, as worry may set in. Medical science doesn’t help much in this case. It offers us medicines for a full night’s continuous sleep, which sounds natural; however, according to Warren’s theory, it is really the opposite of what we need.

小题1:The late night was called “The Watch” because it was a time for people ______.

A．to set time to catch animals

B．to remind others of the time

C．to guard against possible dangers

D．to wake up their family and neighbors小题2:We can infer from the last paragraph that people should ______.

A．sleep in the way animals do

B．follow their natural sleep rhythms

C．keep to the eight-hour sleeping way

D．ask doctors for help if they can’t sleep小题3:What is the writer’s purpose in writing the passage?

A．To throw new light on human sleep.

B．To encourage people to sleep less.

C．To give some suggestions on insomnia.

D．To find out people’s hibernating history.

水结冰后，冰能浮在水面上，这个事实说明____________。

小明为了探究惯性现象，在行驶的车厢中用细线悬吊一小球，用以观察车厢的运动变化情况，请写出他观察到的现象的结论．

（1）若小球在竖直悬线下保持静止，则车厢在做______运动；

（2）若小球突然向正后方摆动，则车厢在做______运动；

（3）若小球突然向正前方摆动，则车厢在做______运动；

（4）若小球突然向右摆动，则车厢在做______运动；

（5）若小球突然向左摆动，则车厢在做______运动．

在无端蓄电池的情况下，铅酸蓄电池每个蓄电池的均衡充电电压一般为（）V。

A.2.15～2.25

B.2.25～2.35

C.2.35～2.45

D.2.45～2.65

滑动轴承胶胎的主要原因是什么？