(一) can/could

　1. 表示能够做某事(具备某种能力)(could主要指过去);

　2. 表许可; 用于疑问句表示请求(could表示语气更加婉转);用于否定句表示不允许。

　3. can还可表一时的可能性。

　考例1

　I’m going to Europe on vacation together with John if I ______ find the money. (2012全国II)

　A. can B. might C. would D. need

　解析：Acan在句中意为“能够”。

　考例2

　Peter ______ be really difficult at times even though he’s a nice person in general. (2008辽宁)

　A. shall B. should C. can D. must

　解析：Ccan在句中表“可能”。

　(二) must

　1. must用于肯定句中表示说话人的意志或义务，或者坚决要求某人做某事，意为 “必须”;mustn’t表示“禁止”。

　2. 在以must开头的疑问句中，肯定回答用must;否定回答用needn’t 或don’t have to，表示“不必”。

　3. 另外还有一种含义为“偏要”。表示说话人生气或不满的情绪。

　考例1

　—Shall I inform him of the change of the schedule right now?

　—I am afraid you ______, in case he comes late for the meeting. (2011福建)

　A. will B. must C. may D. can

　解析： B。must意为“必须”。

　考例2

　—______ you interrupt now? Can’t you see I’m on the phone?

　—Sorry Sir, but it’s urgent. (2012重庆)

　A. Can B. Should C. Must D. Would

　解析：C。must在句中意为“偏要，非要”。

　(三) will / would

　will (would) 表意愿, 用于各种人称的陈述句，还可表示某种习惯，或在疑问句中提出请求。主语为物时，可意为“不起作用”。

　考例

　Days later, my brother called to say he was all right, but ______ say where he was. (2012江苏)

　A. mustn’t B. shouldn’t C. wouldn’t D. mightn’t

　解析：C。would在句中为will的过去式，表意愿。

　(四) may / might

　表示允许，和can/could一样，可用于各种人称。但要注意：在疑问句中will/would表示征询对方许可或提出请求时，常用于第二人称, would / might/could形式常表语气委婉，不表示过去时态。

　考例

　—______ I take the book out?

　—I’m afraid not. (2010四川)

　A. Will B. May C. Must D. Need

　解析：B。will/would 用于第二人称表示“请求”;而may可用于各种人称。

　(五) shall/should

　1. shall用于二、三人称，表示“命令、威胁、警告、强制、允诺”等。

　2. 在疑问句中， shall用来征询意见或请求指示，用于第一和第三人称。

　3. shall常用在主语是第三人称的条约、法律法规、规章制度等文件中表示“义务”或“规定”。

　4. should 用于劝告、建议的目的时，可译成“应该”，表示主观情况。

　考例

　One of our rules is that every student ______ wear school uniform while at school. (2012辽宁)

　A. might B. could C. shall D. will

　解析：C。shall在句中表示“义务”或 “规定”，意为“应该，必须”。

　考点二、表推测的情态动词

　(一) 对现在的情况或客观事实推测

　1. 对现在或客观事实的肯定推测

　must意为“肯定、准是、想必是”;should意为“很可能、该……”，指按常理推测;may(might)意为“也许、大概”，表示把握不大的推断;can/could可用于疑问句表示怀疑(could则表示更不确定);could还表示现在或将来的可能性。

　考例1

　—What are you doing this Saturday?

　—I’m not sure, but I _____ go to the Rolling Stones concert. (2013重庆)

　A. must B. would C. should D. might

　解析：D。might意为“可能”。

　考例2

　—Good morning. I’ve got an appointment with Miss Smith in the Personnel Department.

　—Ah, good morning. You _____ be Mrs. Peters. (2010北京)

　A. might B. must C. would D. can

　解析：B。答语句意：哦，早上好。你一定是Peters夫人了。

　2. 对现在情况或客观事实的否定推测

　can’t意为“不可能”、“想必不会”，表示推测的语气相当有把握;couldn’t也可有此用法，但语气委婉。 may not, might not意为“可能不”、 “也许不”，表示推测的语气不很有把握。

　考例

　It ______ be the postman at the door. It’s only six o’clock. (2011江西)

　A. mustn’t B. can’t C. won’t D. needn’t

　解析：B。句意：门口的不可能是邮递员，现在只有六点钟。

　(二)对过去情况的推测

　1. must have done过去一定做过某事;

　2. can’t have done/couldn’t have done过去不可能做过，肯定没做过某事;

　3. can/could have done用于疑问句中表示对过去发生的事情或状态的推测;

　4. could have done 过去可能做过某事;

　5. may / might (not) + have done过去可能(没)做过某事。

　考例

　Since nobody gave him any help, he _____ have done the research on his own. (2013课标2)

　A. can B. must C. would D. need

　解析：B。句意：因为没有人给予任何帮助，他一定是独立完成这项研究的。

　考点三、“情态动词+have+过去分词”的其他用法

　1. should /ought to have done表示过去本应该做某事却没有做。

　2. shouldn’t /ought not to have done 表示本不应该做某事却做了。

　3. could have done在肯定句中还可表示“本来可以/可能做成某事”。

　4. might have done可表示本来可能，但实际上没有发生的事。

　5. needn’t have done表示“本来不需要做某事而做了”。

　考例

　We ______ the difficulty together, but why didn’t you tell me? (2012北京)

　A. should face B. might face C. could have faced D. must have faced

　解析：C。句意：我们本可以一起面对困境的，可是你为什么不告诉我呢?

I work with Volunteers for Wildlife, a rescue and education organization at Bailey Arboretum in LocustValley. Trying to help injured, displaced or sick creatures can be heartbreaking; survival is never certain. However, when it works, it is simply beautiful.

我在“野生动物志愿者”组织工作，这是蝗虫谷贝利植物园的一个援救教育组织，帮助受伤、流离失所或生病的动物。这样的工作可能会令人心碎；因为无法确定动物是否能活下来。然而，当救援起作用时，这种感觉真的很棒！

I got a rescue call from a woman in Muttontown. She had found a young owl on the ground. When I arrived, I saw a 2-to 3-week-old owl. It had already been placed in a carrier for safety.

我接到马特顿镇一位女士的求救电话，她在地上发现了一只猫头鹰幼鸟。当我到达时，我看见了一只两三周大的猫头鹰。为了安全起见，它已经被放在一辆大货车上。

I examined the chick and it seemed fine. If I could locate the nest, I might have been able to put it back, but no luck. My next work was to construct a nest and anchor it in a tree.

我检查了这只幼鸟，看起来还不错。如果我能找到鸟巢，我也许能把它放回去，但没那么幸运。接下来的工作就是建造一只鸟巢，并固定在一棵树上。

The homeowner was very helpful. A wire basket was found. I put some pine branches into the basket to make this nest safe and comfortable. I placed the chick in the nest, and it quickly calmed down.

房主非常乐于助人，给我找来了一只铁丝篮。为了让鸟巢安全舒适，我把一些松枝放进铁丝篮里，然后我把小猫头鹰放进鸟巢里，它很快安静了下来。

Now all that was needed were the parents, but they were absent. I gave the homeowner a recording of the hunger screams of owl chicks. These advertise the presence of chicks to adults; they might also encourage our chick to start calling as well. I gave the owner as much information as possible and headed home to see what news the night might bring.

现在最需要的是这只小猫头鹰的父母，但它们不在。我给了房主一份小猫头鹰饥饿尖叫声的录音。这些录音会让猫头鹰父母知道小猫头鹰的存在，也会鼓励小猫头鹰学着尖叫。我把尽可能多的消息告诉了房主，然后回家，看看晚上会有什么情况。

A nervous night to be sure, but sometimes the spirits of nature smile on us all! The homeowner called to say that the parents had responded to the recordings. I drove over and saw the chick in the nest looking healthy and active. And it was accompanied in the nest by the greatest sight of all — LUNCH！The parents had done their duty and would probably continue to do so.

这的确是一个紧张的夜晚，但有时大自然的神灵会眷顾我们！房主打电话说小猫头鹰的父母已经对这些录音做出了回应。我开车过去，鸟巢里的小猫头鹰看起来健康又活泼。鸟巢里出现了最令人感动的一幕——小猫头鹰的身边全是午餐！它的父母已经在尽职尽责，而且很可能会继续这样做。