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I will not go unless I hear from him.
如果我不收到他的来信,我就不去。
[特别提醒] unless连接一个条件从句,等于if…not, 不同点在于:if …not是口语, unless为书面语,unless有否定意思。例如:
I shall go there unless it rains.
= I shall go there if it doesn’t rain.
我去,除非下雨(如果不下雨,我就去)。
但在下列情况下二者不能换用:
1)表示“由于未发生B而发生A”的句子只能用if…not, 而不用unless。例如:
I’d be glad if she doesn’t come this evening.
如果今天晚上她不来我将很高兴。
2)if…not可以引导一个虚拟条件句,unless一般不引导虚拟条件句。例如:
If she weren’t so silly, she would understand.
如果她不那么傻,她就会明白了。
[跟踪练习]
1. You won’t catch up with your classmates ____ you work harder.
A. and B. or
C. unless D. if
2. The sports meet will continue ____ it rains this afternoon.
A. if B. since
C. as soon as D. unless
Key: 1.C 2.D
