Tea wasn't introduced into Europe until the early 17th century. And now it has _______ popular in Europe and America.这道题给的答案是become，请问可不可以用been呢？如果不行，为什么呢？
...n be transported from long distances and stored until we need it, first in the supermarket, and then at home.这句话里的we can be transported的被动语态为什么要用在we上啊？不是应该用在packaged or canned food上吗？
Greater demands were being placed on the police by growing violence and left and right-wing extremism. 不断增加的暴行和左翼右翼极端主义使得需要更多警力。老师：您好！这句话我没理解（1）为啥这里要用were being placed on 这个时态（2）我没理解这个...
请分析句子成分，主要是逗号以后部分:It took him about ten minutes to make the trip each time, a delay sufficiently irritating that Obama’s assistant expended considerable effort to avoid it.
When the Revolutionary War was over, General Washington wanted to go home to his Virginia estate, called Mount Vernon.上文中过去分词called只表示被动但我没有看出来过去分词发生的时间在谓语动词之前？请老师讲解一下，非常感谢。（听曹老师讲解过，...
...的，请老师解惑，谢谢。例句，I would never have believed it. They have accepted the whole scheme.上文中的it是前照应，可是为什么与后面的整个句子照应，而不是与前面文章中的某物照应呢？（我认为前照应该是与前面的文章照应，而不应...
More than two million candidates have signed up for the upcoming exam around China, a 13.6 per cent increase from 2016, according to enol.cn.看着像是 more than two million candidates 的同位语，不知我理解对不对。