Tom has been out of work for two years, so he has difficulty______.

A．earning living

B．earning his living

C．to earn livings

D．to earn his living

废水中的氰化物可用( )去除。

A．(A) 空气氧化法

B．(B) 沉淀法

C．(C) 混凝法

D．(D) 氯氧化法