词组 | can(be able to) |
释义 | can : be able to — 194 1a. 由于 can 这一助动词没有完成式和将来式,在需用这两种时态的时候,往往改用后者这个复合助动词来代替(参见词目 195 );甚至一般过去时态也用它来代替,不用 could (注:因为 could 含有情态色彩)。 例如: We have been able to produce new-devised sewing machines. 我们已能生产新设计的缝纫机了。(用于现在完成时态) They were able to quicken their steps towards achieving theobjective. 他们已经能够朝着目标加快步伐了。(用于一般过去时态) Shall you be able to come tomorrow? 你明天能来吗?( =Will it be possible for you to come tomorrow? ) 1b. 用于一般陈述结构,后者含有“使之能干”或“得以”的义蕴,相当于 manage to do 的意思;因此,也不宜使用 can / could 。——当然,用于否定的陈述结构则不在此限。 例如: He studied very hard, and was able to pass his examination. 他读书很用功,所以能够考得上。(不说… could pass his examination ) We had holidays yesterday and so were able to return home again. 我们昨天放假,所以得以再回家一次。(也不说… and so could return home again ) 比较: He studied very hard, but wasn't able to/couldn't pass hisexamination. 他读书很用功,但考试没考上。(用于否定句,两者可以通用) He studied very hard, and was able to pass his examination. 他读书很用功,所以能够考得上。(用于肯定句,不能改用 could ) |
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