Once lost,such a chance might never come again
是Once it is lost,such a chance might never come again
主句是such a chance might never come again
其主語是a chance,而once it is lost這里的It也是指這個(gè)chance,前后兩個(gè)句子是相同的主語,因此可以省略掉it is,或者說省略掉the chance is
A.it is hard to get such a chance again once it is lost.
主句主語是to get such a chance 要得到這么一個(gè)機(jī)會(huì),是to do sth.跟后面的it (指chance) 是不一樣的主語,這時(shí)候it is 不能省略掉
B.to get such a chance will be defficult once it is lost 道理跟上面的一樣,前面的主語是to do sth.
C.one can nerver get such a chace again once it is lost.這里的主句說的是一個(gè)人不能再得到這么一個(gè)機(jī)會(huì),反正說的主語也不是chance.
綜上,就是選D了.