Question

英语高手进

When I try to understand----that prevents so many Americans from being as happy as one might expect,it seems to me that there are two causes.为什么填what it is感激

Answer 1

what引导宾语从句，宾语从句是一个强调结构，what 又作为被强调的部分，意思是我想知道到底是什么让美国人无法像他们期望的那样幸福，在我看来有两个原因。

Answer 2

这是个强调句型，你把it is that 去掉后，就可以看出这个完整的句子意思了，

Answer 3

宾语从句，有两个宾语从句