填埋场应至少位于居民区（）以外。A.100m B.200m C.400m D.500

Thousands of years ago, people didn't live in cold places because they didn't know how to keep themselves warm. Later they learned to make clothes. When an animal was killed, they made use of its skins to cover their bodies.    小题1:  .

小题2:   . It once helped people find fire, when lighting hit a forest and started a fire.    小题3:    The fire kept them warm, and also frightened wild animals. Soon people found the food cooked tasted much better, so they began to use the fire to cook food.

But people still didn't know how to make a fire. When they got a fire from the forest they tried to keep it burning.    小题4:

But later they found different ways to make fire. For example, they made fire by burning wood or knocking two pieces of stones.

Today it's easy for people to make fire because they have matches, lighters and different kinds of heaters.    小题5:

根据短文内容，把A-E五个选项填入文中空缺处，使短文内容完整、正确。

一些同学乘坐高速列车外出旅游，当火车在一段平直轨道上匀加速行驶时，一同学提议说：“我们能否用身边的器材测出火车的加速度？”许多同学参与了测量工作，测量过程如下：他们一边看着窗外每隔100m的路标，一边用手表记录着时间，他们观测到从第一根路标运动到第二根路标的时间间隔为5s，从第一根路标运动到第三根路标的时间间隔为9s，请你根据他们的测量情况，则

（1）火车的加速度大小为______；

（2）他们到第三根路标时的速度大小为______．

要了解某年某地健康成年男性血清总胆固醇水平，则下列说法错误的是（）。

A.研究总体为该地全部健康成年男性的血清总胆固醇含量

B.观察单位是每个人

C.该研究的同质基础是同一地区、同一年份、同为男性健康成人

D.该研究总体属于无限总体

E.该研究适宜进行抽样调查研究

与肌萎缩性侧素硬化相鉴别，脊髓空洞症的特点是（）

A.节段性分离性痛温觉缺失

B.肌束震颤

C.双手肌肉萎缩

D.MRI可显示空洞

E.锥体束症

可编程序控制器的主机各部分之间通过（）进行连接

A、内部系统总线

B、电缆

C、电源总线

D、控制总线