bob is not promised to join in the football match____ he has to help his parents on the farm
问题描述：
bob is not promised to join in the football match____ he has to help his parents on the farm
A、if
B、as
C、unless
D、when
答
if是如果的意思
as是因为的意思
unless是除非的意思
when是当的意思
这句话的意思是“鲍勃没有承诺在参加足球比赛,因为他帮助他的父母在农场”
所以选B