转向系主要性能参数有：转向器的效率和（），转向系的角传动比和（），以及转向系的刚度与转向盘的旋转圈数。
参考答案：啮合间隙；力传动比
动词填空。
1. What a beautiful picture! Can it ________ (put) up at Christmas?
2. —Where's my pen? —I just ________ (put) it here on the desk.
3. Mum told me spring ________ (follow) winter.
4. She ________ (listen) to the English program when I went to see her yesterday.
5. —Don't park here. —Sorry, I ________ (not see) the sign.
我国规定适用于一般环境的安全电流为（）。
A.25mA
B.30mA
C.40mA
D.50mA
