牛津实用英语语法 337 in case和lest
A in case
1 in case+主语+动词可跟在陈述句或命令句后面:
I don’t let him climb trees in case he tears his trousers.
我不让他爬树,以免撕破裤子。
句子的第一个动作常常是为if从句中的动作所做的准备或是对它采取的预防措施。if从句表示将来可能发生的动作。in case+一般现在时常意为because this may happen/because perhaps this will happen/for fear that this may happen(因为这大概会发生/因为这也许将会发生/以免它会发生)。
in case+一般过去时常意为because this might happen/be- cause perhaps this would happen/for fear that this would happen (因为这会发生/因为这将会发生/以免它会发生)。
在这里,无论现在时或过去时都可用should+动词原形来代替。should在此表示更小的可能性,但是这种结构不常见。
2 各种时态与in case连用
I’ll make a cake in case someone drops in at the weekend.
我将做个蛋糕以免有人周末来。
I carry a spare wheel in case I have/should have a puncture.
我带了个备用轮胎,以免车胎被刺破。
I always keep candles in the house in case there is a power cut.
我家里常备有蜡烛,以防断电。
I always kept candles in the house in case there was a power cut.
我家里以前常备有蜡烛,以防断电。
(另参见第227节。)
B lest意为for fear that(恐怕),后面跟should:
He doesn’t/didn’t dare to leave the house lest someone should recognize him.
他不敢出门,怕有人认出他来。
lest除在较正式的书面英语中出现外,一般不常用。