核心问题
请讲一讲 at a time 与 at the time 这两个介词短语的区别。
词典解答
at a time 意为“一次(at a single time)”，而 at the time 意为“那时(候)”“当时”。请对比下列例句：
- You can borrow only five books at a time.
一次只可借5本书。
- He picked up the books one at a time. (Wood)
他一次一本地把书都拾了起来。
- Jackson called at the office this afternoon, but I could not see him, as I was engaged at the time. (Wood) 杰克逊今天下午到办公室来了，但我当时正在忙，没能见他。
(参见 at a time/at one time)