11.(2010天津) Mark _______ have hurried. After driving at top speed, he arrived half an hour early.
A. needn’t B. wouldn’t C. mustn’t D. couldn’t
答案：A
解析：本題考查情態(tài)動(dòng)詞的用法。句意“馬克本不必那么匆忙。他極速行駛，最后早到了半個(gè)小時(shí)”。needn’t have done本沒必要做，但是做了；couldn’t have done表示過去不可能做了某事；wouldn’t have done用在表與過去試試相反的虛擬語氣中；mustn’t表禁止，不用在此結(jié)構(gòu)中。

12.(2010湖南) You _______ buy a gift, but you can if you want to.
A. must B. mustn’t C. have to D. don’t have to
答案：D
解析：本題考查情態(tài)動(dòng)詞的用法。句意“你不必買禮物了，但是如果你愿意的話也可以買”。根據(jù)句意可以此處須用否定形式，故排除A、C項(xiàng)；mustn’t表示禁止；don’t have to意為“不必……”。故答案為D項(xiàng)。

13.(2010江蘇)?-- I haven’t got the reference book yet, but I’ll have a test on the subject next month.
-- Don’t worry. You _______ have it by Friday.
A. could B. shall C. must D. may
答案：B
解析：本題考查情態(tài)動(dòng)詞的用法。句意“我至今還沒有拿到參考書，但是下個(gè)月這個(gè)學(xué)科就要測(cè)試了?！薄皠e擔(dān)心，周五之前你一定會(huì)有的?！眘hall用于第二人稱表示允許、要求、命令、威脅等語氣，根據(jù)句意可以此處表示允許的語氣，故答案為B。could能，能夠；must必須；may也許，均不符合語境，可排除。

14.(2009北京) One of the few things you _______ say about English people with certainty is that they talk a lot about the weather.
A. need B. must C. should D. can
答案：D
解析：本題考查情態(tài)動(dòng)詞的用法。句意“對(duì)于英國(guó)人妮可以確定的為數(shù)不多的事情之一就是他們對(duì)天氣談?wù)摰煤芏唷?。Can意為“可以”；need意為“需要”，用作情態(tài)動(dòng)詞是常用于否定句、疑問句；must意為“必須”；should“應(yīng)該”。

15.(2009全國(guó)II) I can’t leave. She told me that I _______ stay here until she comes back.
A. can B. must C. will D. may
答案：B
解析：本題考查情態(tài)動(dòng)詞的用法。句意“我不能離開。她告訴我在她回來之前我必須呆在這里”。can能夠；must必須；will將要；may可能。

16.(2009遼寧) The traffic is heavy these days. I _______ arrive a bit late, so could you save me a place?
A. can B. must C. need D. might
答案：D
解析：本題考查情態(tài)動(dòng)詞的用法。句意“最近幾天交通擁擠。我有可能遲到一會(huì)兒，因此請(qǐng)你給我留個(gè)位子好嗎？”might往往表較小的可能性，符合句意。can能，會(huì)；must必須，一定；need需要。

17.(2009江蘇) He did not regret saying what he did but felt that he _______ it differently.
A. could express B. would express C. could have expressed D. must have expressed
答案：C
解析：本題考查情態(tài)動(dòng)詞的用法。句意“對(duì)于說出他的所作所為，他并不后悔，只不過他認(rèn)為他本可以用不同的方式表達(dá)”。could have done sth.表示“過去本可以做某事，但沒做”；must have done sth.表示“過去一定作了某事”。

18.(2008北京) John promised his doctor he _______ not smoke, and he has never smoked ever since.
A. might B. should C. could D. would
答案：D
解析：本題考查情態(tài)動(dòng)詞的用法。句意“約翰答應(yīng)他的醫(yī)生不再吸煙了，且從那時(shí)起就再也沒有吸”。Might not可能不；should not不應(yīng)該；could not不可能(表推測(cè))，不能(表能力)；would有“決心，決意”等意思。根據(jù)句意，可知D項(xiàng)正確。

19. (2008上海) According to the air traffic rules, you _______ switch off your mobile phone before boarding.
A. may B. can C. would D. should
答案：D
解析：本題考查情態(tài)動(dòng)詞的用法。句意“根據(jù)航空交通規(guī)則，在上飛機(jī)前，你應(yīng)該關(guān)掉手機(jī)。”should在本句中表示“義務(wù)上”的應(yīng)該。

20.(2008陜西) -- What sort of house do you want to have? Something big?
-- Well, it _______ be big — that’s not important.
A. mustn’t B. needn’t C. can’t D. won’t
答案：B
解析：本題考查情態(tài)動(dòng)詞的用法。句意“你想要什么樣的房子？大一點(diǎn)兒的？”“嗯，房子不必很大——那并不重要”。mustn’t禁止，不允許；needn’t沒有必要；can’t不可能，不能夠；won’t不會(huì)。只有B項(xiàng)符合題意。