题干
It's foggy today. I'm not sure _______ the highway will be closed soon. Let's set off earlier.
A：when
B：whether
C：how
D：that
答案(点此获取答案解析）
B
It's foggy today. I'm not sure _______ the highway will be closed soon. Let's set off earlier.
A：when
B：whether
C：how
D：that
等于（ ）