Unit 4  Learning efficiently

解析：這是混合時(shí)態(tài)、混合語氣的主從復(fù)合句。主句is hard是陳述語氣；賓語從句里的主句謂語would be doing是“與現(xiàn)在事實(shí)不符”的虛擬語氣；if引導(dǎo)的條件句謂語應(yīng)該要是與過去事實(shí)不符的虛擬語氣，因?yàn)閍t the age of seven是明確的時(shí)間狀語。故選b。
2. oh, i’m not feeling well in the stomach. i ______ so much fried chicken just now. (上海)
a. shouldn’t eat     b. mustn’t have eaten    c. shouldn’t have eaten               d. mustn’t eat
解析：時(shí)間狀語just now和過去時(shí)態(tài)連用，因此這是與過去事實(shí)不符的虛擬語氣。故選c。
3. he hesitated for a moment before kicking the ball, otherwise he _____ a goal. (上海)
a. had scored               b. scored              c. would score             d. would have scored
解析：從邏輯的角度看，轉(zhuǎn)折副詞otherwise后面總是要接虛擬語氣。該句中hesitated是過去時(shí)態(tài)，故選d。
4. mr. white _____ at 8:30 for the meeting, but he didn’t show up.  (廣西)
a. should have arrived                        b. should arrive
c. should have had arrived                  d. should be arriving
解析：8:30就應(yīng)到達(dá)，但是現(xiàn)在還沒有出現(xiàn)。should含有輕微的指責(zé)意。故選a。
5. –i’ll tell mary about her new job tomorrow. 23. (福建)
–you _____ her last week.
a. ought to tell             b. would have told               c. must tell           d. should have told 
解析：原因同上。故選d。
6. i was really anxious about you. you _____ home without a word. (全國)
a. mustn’t leave    b. shouldn’t have left    c. couldn’t have left     d. needn’t leave 
解析：你不應(yīng)該一句話不說就離家出走的，但是你卻這樣做了，用虛擬語氣。故選b。
3）與將來事實(shí)可能不符的條件句
if it were to rain this afternoon, the football match would be put off till next friday.如果今天下午下雨，足球賽就推遲到下一周星期五。
did tom come tomorrow(=if tom came tomorrow), we should show him around our campus.如果湯姆明天來，我們應(yīng)該帶領(lǐng)他參觀我們的校園。