吊钳的牙形只有直牙型。
参考答案：错
解析：吊钳的牙形除直牙外还有斜牙和圆弧牙。
用适当的词填空
1. Please write ___ the new words on the blackboard.
2. How ____ milk do we have at home?
3. —____ are you today?
—Fine, thanks.
4. The watch is very nice. ___ you like it?
5. —What's the ____, please?
—It's four.
6. It's time ____ play games. Let's go, Tom.
7. —What's ___ you like to have?
—A glass of milk.
某物体在多个力的作用下处于静止状态，如果使其中某个力F方向保持不变，而大小先由F0随时间均匀减小到零，然后又从零随时间均匀增大到F0，在这个过程中其余各力均保持不变，在下列各图中，能正确描述该过程中物体的加速a或速度v的变化情况的是（ ）
A．
B．
C．
D．
