单项选择题
A.白烟 B.蓝烟 C.灰白烟 D.黑烟
A.活塞裙和活塞销孔 B.环槽和活塞销孔 C.活塞裙和环槽 D.活塞顶和环槽
A.60-120sec B.120-180sec C.180-240sec D.240-300sec