John found it a challenge to meet the needs of the boss.      , he had no way to satisfy him.[ ]

A. In need    

B. In case  

C. In no time      

D. In other words

化学制备的除盐水在进入锅炉之前，应在除氧器（）。

A、除碱

B、除氧、除气

C、除铁