1.—too glad to congratulate you surviving the serious accident! —but you can never imagine how sad and helpless i was ______ so many innocent people lost their lives in the disaster. a. witnessing b. having witnessed c. to witness d. to be witnessed 《解析》c 句意：——很高兴地祝贺你从这次严重的意外中幸存下来。——可是你却永远无法想象，当我看到在这次灾难中那么多无辜的人们失去了生命时我是多么的伤心和无助。题干中imagine的后面是一个由how引导的宾语从句，这个从句的陈述式是：i was sad and helpless to witness so many innocent people lost their lives in the disaster.这个陈述式符合句型“sb./sth.＋be＋adj.＋to do/to be done
