选:A.as popular a language as
解析:as...as...结构中,两个as之间一般是跟形容词,
有时该形容词还可修饰另一名词,但这个名词前应带有不定冠词,
并且要注意词序:as+形容词+a/an+名词+as...
如:She is as good a cook as her mother .
=She is a cook as good as her mother.
她和她妈妈一样,是位好厨师.
但不能说:She is as a good cook as her mother .
因此,此题选A.