小测验：选择正确的单词

1. gravity fault
   重力断层，正常断层
   
2. gravity gradient
   重力梯度
   
3. gravity meter
   重差计，重力仪
   
4. gravity wave
   重力波
   
5. specific gravity
   比重，比重值
   
6. center of gravity
   n. 重心
   
7. centre of gravity
   重心 【化】 重心
   

1. The stone rolled down the hill by gravity.
   石头在重力作用下向山下滚去。
2. That the earth has gravity is clear .
   很清楚地球是有引力的。
3. He could hardly keep his gravity.
   他忍不住要笑出来。
4. I don't think you understand the gravity of the situation.
   我想你不了解局势的严重性。
5. The law of gravity is universal.
   引力定律适用于宇宙万物。

　3个名词解释