调整气阀间隙时，要求滚轮落在凸轮的基圆上，摇臂、顶杆和顶头之间保持接触。
A、基圆、间隙
B、定圆、接触
C、基圆、接触
D、基圆、间隙
参考答案：C
the responsibilities of the family, I worked hard to earn a living.
A．Being burdened with
B．Burdened with
C．Burdening with
D．To burden with
光纤的主要传输特性有哪些？
