【题目】If he had known he was building his own house，he all of it so differently.
A. would do B. would have done
C. could do D. must have done
在线课程【答案】B
【解析】根据“If he had known”可知，本句是对过去的虚拟，因此主句中谓语动词需用would have done结构。must have done表示“一定做过”，是过去事情的肯定推测。