where did you find Xing Ming? It was in the office____ he worked. A this B which C where D / 请教孙老师为何选B，不选C？

上面的答都不合适，用that比较好。 ．it引导的强调句型，通常形式为：It＋be＋被强调部分＋that／who＋其它。这种强调句由普通陈述句转换而来，用来强调句子的主语、宾语或状语。例如： Karl bought Marva a bicycle on her birthday．卡尔在玛瓦生日那天给她买了一辆自行车。 It was Karl that／who bought Marva a bicycle on her birthday．（强调

上面这题是强词句，但是强调部分应该是没写出来，而填的空是定语从句才对啊。补充完整是:It was in the office ____he worked that I found Xing Ming.所以空里应该填where 或in which　才对啊。而您在讲定从与强调句的区别里给的答案却是B，所以还是没搞清楚，请您再给解释一下，将不甚感激！！！！