1道英语单选--Please tell me _____ you know whether they have climbed the top of the mountain or not.--I'll call you.OK?a whenb how选什么?为什么?

1道英语单选--Please tell me _____ you know whether they have climbed the top of the mountain or not.--I'll call you.OK?a whenb how选什么?为什么?
1道英语单选
--Please tell me _____ you know whether they have climbed the top of the mountain or not.
--I'll call you.OK?
a when
b how
选什么?为什么?

1道英语单选--Please tell me _____ you know whether they have climbed the top of the mountain or not.--I'll call you.OK?a whenb how选什么?为什么?
A
因为这句话的意思是
——当你知道他们爬上山或没有请告诉我.
——我将会告诉你.好不?
所以应选A