Which of the following is NOT part of the nitrogen cycle?

PLEASE HELP

The answer is atmosphere. there are four spheres of the earth: 1. geosphere (from greek word 'geo' = ground), 2. hydrosphere (from greek word 'hydro' = water), 3. biosphere (from greek word 'bio' = life), and 4. atmosphere (from greek word 'atmo' = air). a magnetosphere is a region of space around astronomical objects controlled by the magnetic field of that object. through the process of elimination, since lightning is present in the air, it can be found in the atmosphere.

My pigs teeth have already came in years ago, with my first molars, and my second molars are pretty much in. my wisdom teeth will be unable to come in, but i'm getting those out on monday.