Question

That their decision was the best one is arguable what we need here is some new people with new idea

为什么第二句要用what不用that 答案说名词性从句缺主语 谁能告诉一下哪部分是从句 我怎么觉得它不却成分呢？ 谢谢大家
That their decision was the best one is arguable
what we need here is some new people with new idea

Answer 1

1）That their decision was the best one is arguable 这一句补完如下：
That their decision was the best one,that is arguable.
这是个定语从句。that后的从句修饰the best one，在句中作主语。
2）what we need 是个名词从句，是一个惯用语法，意思是“什么”，用that 没有这层意思在里面。整句话是：什么是我们所需要的？新人新思想。

Answer 2

他们的决定是最好的是不会有我们这儿需要的是一些新人的新主意

Answer 3

他们的决定是最好的是不会有我们这儿需要的是一些新人的新主意

Answer 4

what we need here是从句中充当句子主语的部分we need后面还缺成分所以只能用宾语