As is known to us of all,Hangzhou is________ a beautiful city.
A.famous for B.well known for C.famous as D.well known for
选哪个啊。为什么？谢谢你的帮助。

be famous for 与 be known for 有什么区别？be famous as 与 be known as又有什么区别？
几乎没有区别 用起来是一样的 都是表示“闻名”
不过一般在情感意义上有点细微区别
be famous后面一般都是好的词语 比如中国因为长城而闻名
北京因为奥运而闻名
但be known就不一定是好词了
比如He is known for his greed. 他因为贪婪而出名

be famous for 与 be famous as
这一对短语都是“以……而出（著）名”的意思，但两者的主要区别是：for 是“因为……而出名(原因)”，as 是“作为……而出名(具体事物)”。例如：

Einstein was famous for his Theory of Relativity.
爱因斯坦以他的相对论而著名。

Einstein was famous as a great scientist.
爱因斯坦以一位伟大的科学家而著称。

Scotland has many lakes and mountains, and is famous for its beautiful countryside.
苏格兰有许多湖泊和山脉，并以其乡村美景著称。

The area is famous as a green tea producing place.
这个地区以绿茶产地而出名。

This grammar book is famous for its practical usage.
这本语法书以其实用性而被人所知。

This book is famous as a reference book.
这是一本有名的参考书。
根据句子的意思可知，选C，as 是“作为……而出名(具体事物)”