• # question_answer Atmospheric nitrogen can undergo nitrogen fixation by 1. cynabacteria 2. Lightning 3. Ultraviolet rays Select the correct answer using the codes given below. A)  1 only   B)  1 and 2 only C)  1 and 3 only      D)  1, 2 and 3

[d] Nitrogen fixation (NF) is a process in which nitrogen $\left( {{N}_{2}} \right)$ in the atmosphere is converted into ammonium $\left( N{{H}_{4}}+ \right).$ Nitrogen fixation occurs naturally in the air by means of lightning. Biological nitrogen fixation is carried by cyanobacteria (e.g. the highly significant Trichodesmium and   Cyanothece),   green   sulphur   bacteria, Azotobacteraceae, rhizobia and Frankia. NF also takes place in presence of UV rays.