The teenager seemed to be a good driver; _____, I didn't dare to travel in his car.   [ ]

A. therefore

B. so

C. even though

D. even so

收球时，排污或放空管线颤抖的厉害，应采取（）的方式解决。

A.增大推球的压力

B.增加排污或过空气量

C.减小推球气量

D.A+B+C