Correct option is C
Temperature inversion occurs when the temperature of the atmosphere increases with altitude, contrary to the normal decrease with altitude. In a temperature inversion, a layer of cooler air at the surface is trapped by a layer of warmer air above. This phenomenon can lead to several atmospheric effects, including trapping pollutants near the ground and affecting weather patterns.
Option a is incorrect as temperature inversion specifically refers to a change in the normal temperature gradient.
Option b is incorrect as it does not specify the inversion condition.
Option d is incorrect because it describes the normal temperature gradient where temperature decreases with altitude.
Thus, the correct condition describing a temperature inversion is that the temperature always increases with altitude during an inversion.
