Question

I _____ you somewhere before , but your name has escaped me _____ moment .

1. A.
   must see ; for a moment
2. B.
   must have seen ; for a moment
3. C.
   must see ; for the moment
4. D.
   must have seen ; for the moment

Answer 1

D
must與不定式的完成體連用表示對(duì)過(guò)去發(fā)生的事持肯定態(tài)度的推斷，在疑問(wèn)句中用can，在持否定態(tài)度的推斷時(shí)用can not 。例如：He must have rid himself of his preumonia last week , for you see , he doesn't cough at all now . (他在上星期肯定治愈了他的肺炎，你看，他現(xiàn)在一點(diǎn)都不咳嗽了。) for a moment表示一個(gè)動(dòng)作延續(xù)了一會(huì)兒，而for the moment 則表示"目前；暫時(shí)"。