A.活塞在下止點(diǎn)之前 B.活塞在下止點(diǎn)之后 C.活塞在上止點(diǎn)之前 D.活塞在上止點(diǎn)之后
A.120° B.240° C.360° D.480°
A.120° B.240° C.360° D.180°