can和be able to表能力,He can watch TV now. He can watch TV tomorrow.前一句可以用be able to的现在一般时替换,后一句可以用现在将来一般时替换. 这个很好理解. 那么问题来了,must和be sure to表必定的推测时,He mu...
The challenge we face is to find ways to meet the needs of our growing
population while _______(protect) the environment.这里填protecting是省略了主语和be动词吗?但是主语不是the challenge吗?
老师您好,请问used to be这种结构(过去是、曾经是)是否可以接确认性表语,表特指某一独一无二的人或物?比如:She used to be the
intellectual girl whom we were all appreciated.Shantou used to be the
economically backward city.(自己造的句子)谢谢...