1 再问关于until,unless的试题

I didn't believe I could do it___I got to the top of Mount Tai.

A until   B unless

A答案正确,但是B答案错误的充分理由?

另,题干中的could是否应该改为was able to,因为这是过去特定的‘能’,与具体事件有关。

盼专家老师详尽权威解答。


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最佳答案 2017-12-23 09:42

就本句而言应选择until。until 和unless 的区别是(注意时态的区别):

1. 用until 可以表示过去已经发生的情况:

I didn't believe I could do it until I got to the top of Mount Tai.

直到我到达泰山顶上,我才相信我能这么做。

2. 用unless 表示一种未发生的假设:

I won’t believe I can do it unless I get to the top of Mount Tai.

我不相信我能做到,除非我到达泰山顶上。

根据所给语境,当然选择until。此外,本句可以用was able to 代替could,表明已经能够做到。关于could和was able to的区别,这是我以前的一个解答,供参考:

【问】我学了情态动词后,觉得对它的用法好像都明白了。可是我最近碰到一个问题,感到情况并非如此。下面就是我遇到的问题,请问:这道选择题,正确答案是选was able to, 我选could为什么不可以?

He didn’t agree with me at first, but I ________ persuade him to sign the agreement later.

A. could        B. might         C. should       D. was able to

【答】在本句中might 和should这两个选项意思都讲不通。实际上就是考查could和was able to 的区别。could表示“(过去)有能力做某事”,was able to 除了这层意思外,还有一个重要的意思,就是:“设法做了某事(managed to do sth.)”,“成功地做了某事(succeeded in doing sth.)”。如果只表达“有能力做某事”这层意思,那么这两个可以互换,而意思保持不变,例如:

He was very strong and he could (=was able to) lift that big stone. 他很强壮,他能够举起那块大石头(意思是他有这个能力)。

但是,如果是第二层意思,那么,只能用was able to,不能用could,例如:

At last he was able to solve the problem.(正)

At last he could solve the problem.(误)

Only when the war was over was he able to get happily back to work.(正)

Only when the war was over could he get happily back to work.(误)

但是,当句子是否定意思时,could和was able to没有差别:

I couldn’t persuade him to sign the agreement. = I wasn’t able to persuade him to sign the agreement.

 

 


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  • quanfa   提出于 2017-12-22 16:08