正确答案是B，that。分析：这个一个强调句，it is .....that(who)句型的考查。选which 是因为以为这个一个定语从句，以为which引导的是修饰bedroom的定语，但其实不是。如果是定语的话，应该是这样：she was sleeping in her bedroom which a thief broke into ，后面就没有the house 啦！the house 和 bedroom重复了这个句子的原型是： a thief broke into the house while she was sleeping in her bedroom（把 it is ..that 去掉，剩下的仍然是一个完整的句...
