1.Half an hour had gone by,but the last bus hadn't come yet.We had to walk home.
半个小时过去了，使用过去式。
2.Mary looks worried about her Chinese exam,because she hasn't learned the text by heart.
发生在过去，对现在产生影响，使用现在完成时。第三人称单数look后加s。
3.Since the basketball game has been postpone,we might as well visit the museum.
篮球赛已经被推迟，使用现在完成时的被动语态。不妨：may as well
4.He stay in Australia with his parents,all the way though World war Ⅱ.
主干：他和父母住在澳大利亚
5.Sinec I graduate from Nanjing University in 1985,I have kinds of lost touch with my classmate.
现在完成时，使用since
