Question

【题目】If you see a flag ___ __ outside a window, you may know someone in that house __ ____ a birthday.

A. fly, have B. flew, has

C. flying, is having D. flying ,has

Answer 1

【答案】C

【解析】

试题分析：句意：如果你看到窗户外面一面旗升起，你可能知道在房子里某个人正在过生日。短语see sb./sth. doing sth.表示看见某人/某物在做某事；主句中的宾语从句缺少谓语动词，这里用现在进行时，其结构是is/are doing的形式，根据题意。故选C。