Only after one has bee a parent how great his parents are．
A. he will realize
B. will he realize
C. that he realizes
D. he does realize
网友回答
A. he will realize
(答案→)B. will he realize
C. that he realizes
D. he does realize
解析：句意：只有一个为人父母了，他才知道父母多么的伟大。Only+副词/介词短语/状语从句，并放在句首的时候，后面的主句用部分倒装，助动词/be动词/情态动词放在主语前面，所以选B。