火花塞间隙过大，发动机易出现（）。
A.低速断火
B.高速断火
C.怠速不稳
D.怠速熄火
参考答案：B
E-mail is very popular today. People seldom write letters now,_______?
A．did they
B．do they
C．didn't they
D．don't they
HSE管理体系的十要素是什么？
