—Do you know ?—Yes. She is doing her homework.A. what is your sister doingB. what your sis

问题补充：

—Do you know ?—Yes. She is doing her homework.

A. what is your sister doing

B. what your sister is doing

C. when your sister is doing homework

D. where is your sister doing homework

答案：

A. what is your sister doing

(答案→)B. what your sister is doing

C. when your sister is doing homework

D. where is your sister doing homework

解析：考查点：考查宾语从句以及句意。解题思路：宾语从句用陈述句语序，根据答句：是的，她正在做作业，可知问句句意：你知道你的姐姐正在干什么吗？故选B。