1. 表示推测：情态动词＋ be＋表：现在状态

                        be doing：现在动作

                        have done：过去

may/might have done：本可以干某事

can/could have done：本能够干某事

should/ought to have done：本应该干某事

needn’t have done：本不必干某事

would/should like/love to have done：过去本想干某事

had better have done：当初最好干某事

would rather have done：当然真该干某事

注：情态动词表推测时，其反意疑问句，应把情态动词变为不是推测的来考虑。

2. 几个情态动词的辨析与特殊用法：

（1）can/could用于肯定句中表“可以”，或“能够”（强调与生俱来的能力）；be able to强调过去设法完成的某一具体的动作。

（2）used to表示过去常常干某事，暗示“现在不干了”，以及表示过去一直存在的状态；would表示过去常常干某事，但不涉及现在的情况，还可以表示过去一直烦人的事情。

（3）need/dare作为实义动词时，应用need/dare to do; 作为情态动词时，一般不用于肯定句中。

（5）will可以表示意愿或必然趋势。

If he won’t help us, all our plans will be ruined.

The window won’t open.

3. 虚拟语气应用于如下结构中：

（1）一种定语从句：It’s time that+did

（2）两种目的状语从句：

so that/in order that+ can/may/could/might +do

（3）三种随时变化句：

①     wish        现在→did/were

      if only   ＋  过去→had done

  as if/though       将来→could/would do

② would rather ＋ 现在/将来→did/were

                 过去→had done

③ 现在：if+did/were, would+ do

   过去：if+had done, would+ have done

   将来：     did

          if+  were to do, would+ do

              should do

注意：除了由if引导的虚拟条件句外，还有倒装条件句，即把were、had或should提前；混合时间句，虚实错综句，以及含蓄条件句，即由or, otherwise, with, without, but for来引导的。

（4）四种名词性从句：

①当表语是important, natural, necessary, possible, strange, arranged, decided, demanded, ordered, requested, suggested, surprising, a pity, no woder时，主语从句要用虚拟语气。例：

It’s important that we (should) help each other.

②动词一坚持(insist)，两命令(command, order)，三建议(advise, propose, suggest)，四要求(ask, demand, request, require)后的宾语从句要用虚拟语气。例：

He insisted that he (should) be sent to the West.

注：insist(坚持说), suggest(暗示，表明)时，从句应用陈述语气。如：

Her pale face suggested that she was ill.

③idea, plan以及表示“坚持，命令，建议，要求”等动词的同源名词作主语时，表语从句用虚拟语气。例：

My suggestion is that we (should) hold a class meeting.

④idea, plan以及表示“坚持，命令，建议，要求”等动词的同源名词后的同位语从句要用虚拟语气。例：

The office gave an order that his soldiers fight back bravely.

巧用上下文语境。①注意上下文的信息提示：信息提示出现在前文时，可以根据前文的信息提示确定答案；信息提示出现在后文时，我们应该先把此空暂时搁置，在理解了后文的基础上，再确定答案。②通读全文，利用复现词语：完形填空试题中，一些词语会重复出现在语篇之中。词汇复现使得语篇中的句子相互衔接，从而构成一个完整的、有机的意义整体。把握这些反复出现的词语，有助于我们确定正确答案。

例1：Reading is a way of learning English without classes or a teacher. It helps develop learners’ independence. And while reading graded readers, learners don’t have to run a____ because the language is at their level.

A. dictionary       B. teacher            C. student            D. recorder

[分析]because在此引导一个原因状语从句，因为读物中使用的语言符合读者的语言水平，读者当然不必求助于词典。

例2：All of a sudden I started to feel rather__1__. She wondered why I was looking for this sort of__2___. I felt even more hopeless when she told me that it would be difficult to get a job without experience.

1. A. encouraged           B. dissatisfied      C. hopeless                   D. pleased

2. A. place                     B. job                  C. advice             D. help

[分析]文章讲到作者去应聘工作，既没有经验又信心，心里感到十分不踏实。从下文中的“I felt even more hopeless”可知第1题填“hopeless”，暗示作者那种无望的心情。而“it would be difficult to get a job without experience”则呼应了第2题，故选job。

例3：Years ago in Scotland, the Clark family had a dream. Clark and his wife worked and____, making plans for their nine children and themselves to travel to  2(America) . It had taken years, but they had   3(finally)  saved enough money and had gotten passports and reservations for the whole family on a new liner t the United States.

A. spent               B. counted           C. saved              D. played

[分析]分析上面一段文字可知Clark夫妇存钱的目的是让一家人出去旅游。根据文中“but they had  3(finally)  saved enough money”可知第1题答案为C项。