—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

对风挡加温系统进行”电源（PWR）”测试时，以下哪个说法正确：（）.

A、测试只能在地面进行

B、只要风挡加温电门放在”ON”位，且”ON”灯熄灭时，就可以进行测试

C、测试电门扳到”PWR”位的时间不能过长，因为此时过热保护不起作用

D、若测试时风挡已处于正常温度，则相应的”ON”灯不会亮