问题
选择题
—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
答案：B
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。