Question

– Look at these factories. I hate them. They____ many rivers here.
--Yes. Something ______ to stop the pollution.

A．polluted, must do	B．had polluted , must be doing
C．have polluted , must be done	D．were polluting, must be done

Answer 1

C

試題分析：句意：看看這些工廠。我討厭它們，它們已經(jīng)污染了很多這里的河水。是的，必須做一些事情來(lái)阻止污染。根據(jù)語(yǔ)境，應(yīng)該用現(xiàn)在完成時(shí)表示已經(jīng)做了某事，一些事情必須被做，情態(tài)動(dòng)詞的被動(dòng)形式must be done,故選C
點(diǎn)評(píng)：動(dòng)詞的時(shí)態(tài)是學(xué)習(xí)英語(yǔ)過(guò)程中非常重要的知識(shí)。現(xiàn)在完成時(shí)表示動(dòng)詞在過(guò)去發(fā)生對(duì)現(xiàn)在造成的影響�，F(xiàn)在完成時(shí)往往和already,yet,for+一段時(shí)間，since+點(diǎn)時(shí)間的時(shí)間狀語(yǔ)連用。一般過(guò)去時(shí)只表動(dòng)詞在過(guò)去發(fā)生，一般現(xiàn)在時(shí)表示習(xí)慣性的動(dòng)詞或是客觀真理、事實(shí)。