If _____, please buy me a backpack while you are at the supermarket.

A．you are convenient

B．it is convenient to you

C．it is convenient with you

D．I am convenient to you

油泵油压不够或没有压力与（）无关。

A.润滑油管太脏

B.油箱内润滑油量过少

C.润滑油酸值过低

D.管道内有气