求，as far as用法！

10． _________, dolphins have no sense of smell.

(A) As known as far

(B) Known thus far as

(C) It is known as far

(D) As far as is known

答案：D

分析：as far as 结构，在托福中是优选项；A，B，C结构错误， 可以用： It is known that dolphins have no sense of smell 。

参考译文：已知，海豚没有嗅觉。

注：实在搞不懂D的结构，为什么？

苦求原因，等。。。。

10． _________, dolphins have no sense of smell.

(A) As known as far>>

(B) Known thus far as>>

(C) It is known as far>>

(D) As far as is known>>

答案：D>>

分析：as far as 结构，在托福中是优选项；A，B，C结构错误， 可以用： It is known that dolphins have no sense of smell 。

参考译文：已知，海豚没有嗅觉。

注：实在搞不懂D的结构，为什么？

苦求原因，等。。。。

as far as (it ）is known, dolphins have no sense of smell.  

这里it =dolphins have no sense of smell不等于dolphins  

当主语太长 为了句子平衡 用形式主语

An example of a species of frog that, at far as is known, has become extinct, is
the platypus frog.

at far as is known 迄今为止已知 做为固定用法记住好了~~呵~~老美估计也讲不出道理来~~