有一读者问：
(1)What we need are more machines.
(2)What we need is more machines.
这两句哪个正确？
上面两个句子都是正确英语，正如下面两个句子都是正确英语一样：
(3)I think what immediately made up his mind were some things Nick Fawley said.
(4)What I'm telling you is mere impressions.
顺便提一下，下面两句也都正确：
(5)All that I have seen are cows and coyotes.
(6)All that I have seen is cows and coyotes.
