关于位移和路程，下列说法正确的是（ ）
A．质点运动的位移大小可能大于路程
B．位移和路程都是矢量
C．质点通过一段路程，位移不可能是零
D．质点运动一段时间，路程不能为零但位移可能为零
A、位移的大小等于初位置与末位置之间有向线段的长度，路程是物体运动路线的长度，位移大小小于等于路程．故A错误；
B、位移是矢量，位移的方向由初位置指向末位置，路程是标量，故B错误；
C、位移取决于物体的始末位置，路程取决于物体实际运动的路径，所以质点运动一段时间，路程不能为零但位移可能为零，故C错误，D正确．
故选：D．
| 完形填空。 | ||||
| What is the population of China? There are more than 1.3 billion people in China. It is 1 one fifth of the world's population. How to control the population growth is a big problem. Some people think it's 2 to control the population growth. But I don't quite agree 3 them because where there is a will, there is a way. The question is how we could 4 it known to everyone how serious the population problems are. Our farmland is becoming less and less to everyone. We have already got too many mouths to feed. 5 we control the population growth, many people will die 6 hunger. Too fast population growth will be bad for our nation. Though laws have been passed to control the population growth, in some places 7 is done to carry out the laws. We should make people 8 that it is foolish of them to give birth to too many children. They should no longer do what they have been doing for many years. We are fighting 9 too fast population growth. Yet the fighting won't end 10 everyone knows its importance and does something for it. | ||||
|