—May I speak to your manager Mr. Williams at five o’clock tonight?

—I’m sorry, Mr. Williams _____ to a conference before then.

A．will have gone

B．had gone

C．would have gone

D．has gone

等质量的铁、镁、铝三种金属与同体积同浓度的盐酸反应，产生相同体积的氢气（相同状况下），下列判断正确的是

A．反应掉的三种金属质量相等

B．反应后三种金属可能都有剩余

C．所给的盐酸都是过量的

D．镁刚好反应完，铁、铝有剩余