only then ____that he had lost a chance of achieving his dream.a he realizedb did he realizedc did he realize 为什么不选b

问题描述:

only then ____that he had lost a chance of achieving his dream.
a he realized
b did he realized
c did he realize
为什么不选b

因为前面已经有了 "did", 所以 "realize" 不需要是过去式.