Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: The process of conversion of nitrogen \((N_2)\) to ammonia by living organisms is called biological nitrogen fixation. Reason R: Nitrogenase enzyme which is capable of nitrogen reduction is present exclusively in Eukaryotes. In the light of the above statements, choose the most appropriate answer from the options given below.