1.(2011全國卷,32) They have arrived at lunchtime but their flight was delayed.
A.will B.can C.must D.should
答案 D
解析:考查虛擬語氣的用法。句意為“他們本該午飯時到達,但他們的航班推遲了。”will have done將來可以完成;can have done可能做過……嗎?表示對過去行為的懷疑,用于疑問句;must have done一定做過某事,表示對過去事情的肯定推測;should have done本來應該做某事,而實際沒做。but their flight was delayed這樣的結果,說明他們本來該到達卻沒有到達,因此選D。