I have experienced quite a number of cases ______ I really wanted to help but could not have anything to ______.
_________ she would have avoided the accident.
Seldom _________ any mistakes during my past five years of teaching in this university.
It was _________ he said _________ disappointed me at that time.
It was only when I reread his poems recently _________ I began to appreciate their beauty.
Hardly _________ the house when he was caught.