Unsatiafied _____ with the payment, he took the job just to get some work experience. [ ]

A. though was he

B. though he was

C. he was though

D. was he though

为什么要在氯乙烯压缩机操作中防止入口管线抽负压（）

A、容易抽入空气而发生爆炸事故

B、避免使压缩机吸气能力降低

C、防止发生液击事故

D、防止压缩机故障