题目

The dictionary is of great use to me. I would gladly have paid for it. A . twice as much B . twice as many C . much as twice D . many as twice 答案：A在四边形ABCD中，若给出四个条件：①AB=BC，②∠BAD=90°，③AC⊥BD，④AC=BD且互相平分．其中选择两个可推出四边形ABCD是正方形，你认为这两个条件是②④或③④②④或③④．（填序号，只需填一组）