有些读者来信都问到一些时态方面的问题，现让我们一并讨论如下：
第一个问题是： 下面两句中的间接引语为什么用过去一般时而不用过去完成时？
(1)The teacher asked us how we liked the story.
(2)The doctor asked when the trouble began.
按照一般语法规则，这两个句子中的间接引语都应用过去完成时，liked应改为had liked, began应改为had begun。实际上，如果都改用过去完成时，也不为错。那么为什么这两个句子偏偏不用过去完成时而用过去一般时呢？
在不会被误会的情况下，间接引语可用过去一般时代替过去完成时。那么，它们之间有无区别呢？ 有，其不同是： 过去完成时强调与主句谓语动词之间的先后关系，亦即强调过去完成时的动作发生在主句谓语动词之前；过去一般时则不强调上述先后关系，而仅强调间接引语叙述的事实。
第二个问题： 下面一些句子对否？
(3)I have seldom gone to the cinema since I bought a TV.
(4)He's never gone to the movies.
(5)I have gone to work by bike since I have had one.
(6)Have you ever gone to New York?
(7)I have already gone there.
(8)I have gone there twice.
(9)No, I have never gone there.
句（3）与句（8）是合乎规范的英语，现在完成时have gone表重复动作。这种用法很普通，再如：
(10)My father has always gone to work by bike.
(11)Twice he has tried and twice he has failed.
(12)It's rained every day this week.
句（4）、（6）、（7）、（9）中的have gone是美国英语，相当于have been。我们认为中国学生应多用have been，少用或不用have gone。句（5）是错句，可改为“I have been going to work by bike since I have had one.”等表重复性动作的句子，这样才能与since（自从）所引导的从句连用。而have gone to work则只表一次性动作，不能与since从句搭配。
第三个问题是： 下面一些句子能成立吗？
(13)I have graduated from college since 1994.
(14)Did you know him before?
(15)Yes, I knew him long ago.
句（13）不能成立，因为graduate不是持续动词，可改为“I graduated from college in 1994. ”; 句（14）正确无误；句（15）也不能成立，因为know是静态动词，不可能与long ago连用，可改为“Yes, I got to know him long ago.”。
第四个问题： 在《英语时态》一书中有这样一句话：
(16)We know each other twenty years.
请问它与
(17)We have known each other for twenty years有何区别？
例（16）用现在一般时，其重点在谓语动词上。例（17）用现在完成时，其重点在for twenty years上。
第五个问题： 下面两句有什么区别？
(18)They told me that you have changed your job.
(19)They tell me that you have changed your job.
例（18）用told，强调未道出的过去某一时刻。例（19）用tell，强调现在的结果或事实。有时现在一般时tell有“认为”的含义，如：
(20)The doctor tells me that I'll soon be right again.
第六个问题： 请问下面两个句子有何区别？
(21)I have been waiting for you for two hours.
(22)I have waited for you for two hours.
例（21）比较口语化，也可能带有不耐烦的感情色彩。例（22）则道出一个事实，仅此而已。
第七个问题： 在下面两句中应填动词be的什么时态形式？
(23)I_________25 next August.
(24)Today is the 19th of November. Tomorrow_________the 20th.
句（23）可填will be或am going to be。句（24）应填will be，因为第二句是从第一句推算来的。
