Some pre-school children go to a day care center, they learn simple English games and song

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A. then
B. there
C. while
(答案→)D. where
解析：考查定语从句。本定语从句的先行词是care center,后面的定语从句很完整，主语是they,谓语动词为learn,宾语是simple English games and songs所以句子里缺少的是状语，故使用关系副词where。