下列关于“质点”的说法中正确的是（ ）
A．体积很小的物体都可以看作是质点
B．转动的物体不可以看作质点
C．只有质量和体积都很小的物体才可以被看作质点
D．在某些情况下，可以不考虑物体的大小和形状，物体就可以简化为一个质点，而与物体的实际质量和大小无关
A、体积很小的物体，如果物体的体积对所研究的问题影响不能忽略，就不能看成质点．故A错误．
B、转动的物体，当物体的转动对所研究的问题没有影响或影响可忽略不计时，可以把物体简化成质点处理．故B错误．
C、物体能不能看成质点，不是取决于物体的质量和体积的绝对大小．故C错误．
D、当物体的大小和形状对所研究的问题没有影响或影响可忽略不计时，物体就可以简化为一个质点，而与物体的实际质量和大小无关．故D正确．
故选D
| 选词填空（用适当形式）。 | |
2. To make sure that he was at home, I ____ him ____ in advance. 3. Just___ with it, and you will succeed. 4. The whole things were ____ , and mother was angry. 5. ____ solving the problem now. 6. She____the water and came up coughing. 7. The shepherd____to look for the sheep that had wandered away. 8. He was very angry and____before I finished my sentence. 9. He was very busy then and promised to ____ later. 10.____ ,he would visit me in the countryside. |