（单词翻译:单击）
Unit1 1 时态、语态(四)
10. Until2 then, his family _____ from him for six months.
A. didn't hear
B. hasn't been hearing
C. hasn't heard
D. hadn't heard
11. Before the first non-stop flight4 made5 in 1949, it _______ necessary6 for all planes to land7 for refueling.
A. would8 be
B. has been
C. had3 been
D. would have been
12. We _____ our breakfast when an old man came9 to the door.
A. just have had
B. have just had
C. just had
D. had just had
答案：
10. D
译文：到那时为止，他家里有六个月没有得到他的消息了。
本句是过去完成时的用法。到过去某个时候(until then)之前，所发生的动作(hear from...),过去完成时常与表示一段时间的状语(for six month)连用。
11. C
译文：1949 年首次直飞以前，所有飞机都需着陆加油。
本句是过去完成时的用法。在过去某个时间之前一直存在的状态，表示过去的过去，所以用过去完成时。
12. D
译文：我们刚吃罢早饭，就有一位老人上门了。
本句是过去完成时的用法。在过去某个时间(come) 之前已经完成的动作(have breakfast) ，表示过去的过去，所以用过去完成时。
