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Only when they met twenty years after graduation ( ) how greatly they had changed.
A、did she realize
B、that she realized
C、has she realized
D、then she realized
【正确答案】：A
【题目解析】：only 置于句首要求倒装，句子含义是直到毕业后二十年详见，她才意识到他们变化了许多。