The right option is; Lightning
Lightning is a way in which atmospheric nitrogen can be changed into ammonia.
Lightning is an extremely fast natural electrical discharge that occurs between a cloud and the ground, or within a cloud usually during a thunderstorm. Lightning can convert nitrogen molecules in the atmosphere into ammonia. Lightning allows nitrogen atom (N2) to react with oxygen (O2) to form nitrogen oxides, which then combine with water to form weak nitric acid (HNO3). Atmospheric nitrogen is released to the earth, and nitrogen is added to the soil in a usable form (such as nitrate). Within plants and other organisms, the nitrates are changed into amino acids and other important compounds.
