问题
I failed again in the examination and only then _____ how much time I had wasted.
A:I realized
B:I had realized
C:did I realize
D:had I realized
B:I had realized
C:did I realize
D:had I realized
正确答案是：
同类题型
Not once________to Michael that he could one day become a top student in his class.(2013·湖南，35)
Another group of Qing Tombs sits about 100 kilometres ______ of Beijing．
Knowledge is there for _______ will seek it
Tom was disappointed because most of the guests________when he________at the party．
My father _______ TV in the living roomwhen I ______ home yesterday.