1. Do you know ________.

A. how many polulations there are in the world.

B. how much population there is in the world.

C. how many the population of the world is 

D. what the population of the world is

答案给的是D。前面刘老师讲过do you know的两种用法，认为do you konw后只能跟that陈述句，或与wh-疑问词连用要后置，那么这个题目本身是不是错误的？

还有这个句子Do you happen to know what size shoes he wears？有问题吗？

2. Why the explosion occurred was that the laboratory attendant had been careless.

此句中的that为什么不能用because替换，都引导表语从句？

3.  I have no idea what the book said. 

what直接引导同位语从句且作said宾语

One of the men held the view that what the book said was right.

此句为什么不直接用what呢，和上面那句区别是啥？我这样理解对不：that在主句中引导同位语，不能省略；what在同位语从句中引导一个主语从句，that和what分别属于不同的主从句？

4._______ is no reason for dismissing her.

A. Because she was a few minutes late

B. The fact that she was a few minutes late

C. Being a few minutes late 

答案是B。 A和C为啥错呢？