分类：教育/科学-升学入学-高考
问题：1.Allflights____becauseoftheterr? 
they had to go there by train.A.having been cancelB.had been canceledC.having canceledD.were canceled
回答：选择A.
这是一个独立主格结构,All flights having been canceled because of the terrible weather,表示they had to go there by train的原因，
首先,这句话表示被动含义,并且是已经完成的动作，故排除C,D，其次,两个完整的英语句子中之间必须要有连词连接,若选择B中间应该加一个连词,个人认为应该是so．