( )you have worked out the first problem,you may go on to work on the second
问题描述：
( )you have worked out the first problem,you may go on to work on the second
( )you have worked out the first problem,you may go on to work on the second
A.even if B.unless C.now that Dthough
答
C 既然,表原因
A 即使,表让步
B 除非,表条件
D 虽然,表让步
既然你已经做出第一道题了,现在可以做第二道了B.unless 为何不对？如果选B除非，应该说才除非你做对第一个题，否则就不能做第二题那后半句应该用否定Unless you have worked out the first problem, you may not go on to work on the second那和时态 have worked out the first problem有没有影响？