Youshouldnotgorafting__________youknowho
题型：选择题
问题：
You should not go rafting __________ you know how to swim, and you should always wear
a life jacket. [ ]
A. though
B. unless
C. until
D. if
You should not go rafting __________ you know how to swim, and you should always wear
a life jacket. [ ]
A. though
B. unless
C. until
D. if