I think it might be Stratosphere, if Ozone layer is an option I will suggest that too.
Answer:
A. Objects whose particles are at the same temperature are in thermal equilibrium.
Explanation:
Kinetic theory of heat is the temperature of a body that is determined by the average kinetic energy of its particles. Objects whose particles experience the same temperature are in thermal equilibrium. Thermal equilibrium means the stability of temperature of an object or no change occur in the body's temperature and the temperature remains the same.
