He failed in his business a third time and only then ______ the difficult situation he was in.
A.I realized
B.I had realized
C.had I realized
D.did I realize
答案:D
He failed in his business a third time and only then ______ the difficult situation he was in.
A.I realized
B.I had realized
C.had I realized
D.did I realize
答案:D