下面这道英语专四语法题 为啥选C不能选择A？

此题命题不够严谨。其实选A语法并没有错，但是考题更偏向于选 C。

A. has been believed to have been
已被认定为过去是。
1. 不定式 to have been 用“完成式”是正确的，表示在谓语动词之前发生。
2. has been believed 是被动语态，意思是“被认为”。现在完成时表示这个看法是过去发生的，后面不定式的动作是“已经被人们认定”已发生了。has been believed 的意思是“已经被认定”。

C. is believed to have been
现在被认为过去是。指现在人们的看法，而且此看法现在仍然存在着。

选择C更加倾向于表达人们现在的看法。

另外，关于 have/has been believed to have done 的例句：
Mount Ararat has been believed to have been the final resting place of the ark, which according to the Bible, came to rest on top of a mountain.
已被公认是方舟最后的安息地。

Officials from EgyptAir say an Airbus 320 plane has been believed to have crashed into sea.
已被认定为落入大海中。

believe为当今之事，故用现在时态。后面才是过去之事，故用不定式的完成式。