下列选项中属于汽车美容的是（）

A.发动机油路清洗

B.发动机舱清洗

C.变速器更换机油

D.发动机机油更换

When the wave period and the apparent rolling period are the same（）.

A.synchronous rolling occurs

B.roll period decreases

C.roll period increases

D.roll amplitude is dampened