The price of the computer is not _____ but cars are very _________.

A．high; expensive

B．expensive; high

C．high;high

D．expensive;expensive

为了防止直升机旋翼因离心力太小造成桨叶拍击，采用了（）

A、挥舞限动块

B、下垂限动块

C、变距摇臂

D、都不是