Question

主谓一致：（并说明原因）All that can be done___.A.has been done B.has done C.have done D.were done

Answer 1

正确答案是 A. has been done.
因为"all" 是第三人称主语，"that can be done"是表语,所以应该用第三人称单数的被动语态, 而"has been done"就是第三人称单数被动语态的形式。
其他的选项都是不合法的，因为主语和谓语不一致
B. has done 是第三人称单数主动语态
C. have done 是第一人称主动语态
D. were done 是第二人称或第三人称复数的过去时主动语态

Answer 2

All that can be done ___. 选D
all,所有的，that can be done是定语从句，修饰all，主语是all,谓语用复数。如果答案给出have been done 也正确。
下边这道题选C。few表复数，指几乎没有人。

Answer 3

当all没具体说是什么的时候，就当做一个整体作单数处理，所以是:All has been done. 一切都被做好了。加一个定语从句，that can be done.

Answer 4

A.
不定代词做主语，谓语动词要用第三人称单数形式

All can be done has been done.