题目内容
In time of serious accidents, _______ we know some basic things about first aid, we can save lives.
[ ]
A.
whether
B.
until
C.
if
D.
unless
答案:C
解析:
解析:
题目内容
In time of serious accidents, _______ we know some basic things about first aid, we can save lives.
whether
until
if
unless