Question

 (2011年南京模擬)People begin to know that most environmental problems exist because necessary measures for preventing them________taken in the past.

A．a(chǎn)re not                         B．were not

C．hadn’t been                  D．wouldn’t be

Answer 1

解析：選B�？疾閯�(dòng)詞的時(shí)態(tài)。句意：人們開(kāi)始了解到由于在過(guò)去沒(méi)有采取必要的預(yù)防措施從而造成了大多數(shù)的環(huán)境問(wèn)題。in the past暗示出用過(guò)去時(shí)態(tài)；hadn’t been指在一個(gè)過(guò)去的動(dòng)作或時(shí)間之前發(fā)生的事情；wouldn’t be表過(guò)去將來(lái)，故B項(xiàng)正確。