1.All flights _B_because of the storm ,they decided to go to Beijing by train.
A having been canceled B had been canceled C having canceled D were canceled
解析:因为航班的取消这动作在他们下决定坐火车去北京之前,所以选择过去完成时态.
翻译：所有的航班因为暴风雨取消了,他们决定坐火车去北京．
2.We shall have completed the work by the time he _B___ back next week .
A will come B comes C is coming D will have come
时间状语从句,从句用一般现在时表示将来.
翻译：我们应该在他下星期回来前把工作都完成．
3.The little girl __A_ into the lake but her father caught her.
A would have fallen B should have fallen C had probably fallen D has fallen
对过去的虚拟语气用法,而should have fallen 表示本应该掉下去,不符合逻辑,只能选择A.
翻译：小女孩没有他父亲及时抓住她的话会掉进河里．
4.---“Do you often swim now ”
-----“No,but I _C___ when I was in my fifties .”
A used to B am used to it C used to do D was used to doing
解析:used to do 的意思是,过去常常做某事,而现在不做了
be used to doing /sth 是习惯于（做）某事 的意思
be used to do被用来做某事
翻译：＿你现在还常游泳吗?
＿没有了,但我50岁时常游泳．
5.A new computer costs about _D____ of this used one .
A the three times price B three time the price C three times a price D three times the price
解析：A is three times the size／price of B句型
翻译：一台新电脑的价格是二手电脑的3倍．