[求助]弱弱的一问What从句的作用

是不是在任何时候what从句的功能都是作名词短语阿？

比如在这句中in the 1980's the rate of increase of the minority population of the United States was nearly twice what it was in the 1970's中就是一个名词性短语；

但是作题的时候我把what it was当作一个主谓结构来看待了，所以错选了其他的答案

而在另一个句子里

last year, land values in most parts of the pinelands rose almost so fast ,and in some parts even faster than what they did outside the pinelands.

A) so fast, and in some parts even faster than what they did

B) so fast, and in some parts even faster than, those

C) as fast, and in some parts even faster than, those

D) as fast as, and in some parts even faster than, those

E)  as fast as, and in some parts even faster than what they did

这题我错选了答案e, 还是把what they did 看作主谓结构了，于是和前面的保持平行，这里它是不是又是相当于一个名词性的短语呢？

请教nn帮我解释一下what引导的从句都有哪些功能吗？

这两个中都是指代错误 it/they 其实what从句本身并没有错