1.How + 形容词/副词
eg:(1) How nice she is!
How + nice (形容词)
原句是：She is nice.
(2) How hard they study!
How + hard (副词)
原句是：They study hard.
2.What + 可数名词复数/不可数名词
eg:(1) What beautiful flowers!
What + beautiful flowers (可数名词复数,注意此处的beautiful用于修饰名词复数flowers)
原句是：The flowers are beautiful.
(2) What nice weather!
What + nice weather (不可数名词,注意此处的nice用于修饰不可数名词weather)
原句是：The weather is nice.
3.What a + 可数名词单数
eg:What a clever boy!
What a + clever boy (可数名词单数,注意此处的clever用于修饰名词单数boy)
原句是：The boy is clever.