1. how引导复数可数名词时，感叹句是怎样变的？

What great inventions he was made！改成how引导的句子如何变呢？

答：只能改成 How great an invention he has made!

不能改成：How great inventions he has made!

2. how 引导不可数名词时，句子怎么变？

What bad weather it is！改成how引导怎么变？

答：可以是：How bad the weather is!

3. The road is crowded. 改成what引导的句子：

是What the crowded road is. 还是what the crowded road it is.

答：可以是 What a crowded road it is!

4. 为什么what引导的感叹句末尾要加it is！而how引导的只加is就可以？

How clean the water is!

What clean water it is!

上面两个句子是对的。第一句之所以不加 it，是因为它有主语 the water；第二句之所以要加 it，是因为句子缺少主语。