as与like的使用方法

One birth-language theory says that our potential for language isinborn but that language itself develops gradually, ____ a function of thegrowth of the brain during childhood.

A. just as     B. like

这里不是接了名词用like吗？为何选A?

as在此为“作为”的意思。出生后语言的进步，是儿童大脑发育的一种功能。这里没比较的意思。