分类：教育/科学-外语学习-英语考试
问题：关于unless从一本书上看到unless这样的说法unless 
从一本上看到unless 这样的说法unless 含有"如果B未阻止,A就会发生"之意,而不可表示"由于B未发生而A才发生"之意的句子.如:I'll be surprised if he doesn't have an accident.此句不可用unless 替换if not请具有相关知识储备的高手指教,我还是对上述陈述理解不好.
回答：请多看一些例句，相信你就会明白的。uns   conj.  除非；如果不； 要是不My baby sister never cries unless she is hungry.我刚出生的妹妹除非饿了，她是从来不哭的。(My baby sister will cry when/if she is hungry.)(If she is not hungry, my baby sister will never cry.)I shall go there tomorrow unless I'm too busy.如果我不太忙，明天将到那儿去。(I shall not go there tomorrow if I am too busy.)(I shall go there tomorrow if I am not too busy.)Unless you go at once you will be late.如果你不马上走，就会迟到的。(If you go at once, you will not be late.)(If you don't go at once, you will be late.)Unless he studies hard, he will never pass the examination.他如果不努力学习, 就永远不能考及格。(If he studies hard, he will pass the examination.)(If he doesn't study hard, he will never pass the examination.)I shall go unless it rains.如果不下雨我就去。(I shall not go if it rains.)(I shall go if it doesn't rain.)