Which one to choose?Why?Thanks.You can guess how i felt_____ i kn_英语解答

Which one to choose?Why?Thanks.
You can guess how i felt_____ i know this.
A.what B.when

人气：153 ℃　时间：2020-05-23 07:09:49

解答

B因为若是它what ,句子必须得有它一个成分.
但是句子没有它的成分,选用when,做时间状语.