To play better, all the players have to know their _______ and weaknesses.

[      ]

A. techniques

B. strengths

C. benefits

D. values

往复式压缩机产生排气量不够的原因（）。

A、吸入气体过脏

B、安全阀不严

C、气缸内有水

D、冷却水量不够