We discussed the high rate of single parent family, and wondered how to explain this . A.

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A. condition
B. state
C. situation
(答案→)D. phenomenon
解析：句意：我们讨论了高比率的单亲家庭，我们不知道如何解释这种现象。phenomenon现象。condition状态；形势。条件；state状况；状态；situation处境；境遇；形势。