另外:
how + 形容词/副词+主语+谓语
what+名词+主语+谓语
How fine it is today!
What a fine day it is today!
how+形容词+(a/an)+名词+be! what+(a/an)形容词+名词!
就是句型上的差异.how更强调形容词;what更强调名词.
What a beautiful day!
How lovely the dog is!这里是你说的那个句子,它有两种表达方法what an useful book they have done!How useful a book they have done!