She ______ have attended that meeting, for she was doing paperwork in the office then.

A．shouldn’t

B．mustn’t

C．wouldn’t

D．couldn’t

30克不纯的铁与足量的稀盐酸反应，产生了1克氢气，则该铁样品中含的杂质可能是[ ]

A．Cu

B．Mg

C．Al

D．Na