问题描述：
At last he ___finishi the work ahead of time.
A.couldB.was able to C.could have done D.would have been able to
请问一下B.D的区别、would have been 的意思是什么、?be able to do 与can do 的区别是什么?wouldn't/won't的用法是什么、?
A.couldB.was able to C.could have done D.would have been able to
请问一下B.D的区别、would have been 的意思是什么、?be able to do 与can do 的区别是什么?wouldn't/won't的用法是什么、?
问题解答：
我来补答展开全文阅读