Which One of the Following Statements Is TRUE Regarding the Nitrogen

Which one of the following statements is TRUE regarding the nitrogen cycle?

A) Nitrogen fixation results in the production of nitrogen from carbon.
B) Atmospheric nitrogen is unavailable to living organisms because two nitrogen atoms are held tightly together by a triple covalent bond.
C) Plants take up ammonia directly from the atmosphere.
D) Once nitrogen is "fixed," it must then be converted to nitrogen gas before living organisms can use it.
E) In a balanced ecosystem, nitrogen fixation occurs more often than denitrification.