In the Process of Nitrogen Assimilation, ____ Is Converted to ____

In the process of nitrogen assimilation, ____ is converted to ____, which is then rapidly used to synthesize organic molecules.

A) NH₄⁺; NO₃^-
B) N₂; NO₃^-
C) NO₃^-; NH₄⁺
D) NH₃; NH₄⁺
E) NO₃^-; N₂