–What do you think of your job, Bob?

–Though ____ flexibility, it is a job____ you are doing something serious but interesting.

A．lacking; where

B．lacking of; which

C．lacking in; when

D．lacking; that

启动机的作用是将电能变成（），带动曲轴旋转使发动机启动。

A.机械能

B.热能

C.动能

D.化学能