The main components of the mesosphere are:
A.\[{{\rm{O}}_2}\] and \[{{\rm{N}}_2}\]
B.\[{{\rm{O}}_2}\] and \[{\rm{C}}{{\rm{O}}_2}\]
C.\[{\rm{N}}{{\rm{O}}^{\rm{ + }}}\] and \[{\rm{O}}_2^ + \]
D.\[{{\rm{N}}_2}\] and \[{{\rm{O}}_3}\]

Hint: Mesosphere is the third layer of the atmosphere, directly above the stratosphere and below the thermosphere. In the mesosphere, strong zonal winds, gravity waves etc. are present. The region is also known as the ionosphere due to formation of ions due to solar radiation.

Complete step by step answer:
-The mesosphere exists just above the stratosphere and troposphere. It starts at about 50km from the surface of the earth and continues till 120km. In this region, the temperature decreases with increasing altitude.
-The upper area of the mesosphere is also known as the ionosphere. During the day, in this part ionisation occurs when nitric oxide is ionised by Lyman series alpha hydrogen radiation. The ionisation is weak and during the night, the free electron and ion again form a neutral compound.
-At an altitude of 95km, green auroras have also been identified in the ionosphere. These are caused by ultra-high speed solar particles interacting with oxygen molecules to form ions. The mesosphere is also the region where meteors burn out and condense to form nuclei for the clouds.
-So, we can conclude that the main components of the mesosphere are \[{\rm{N}}{{\rm{O}}^{\rm{ + }}}\]and \[{\rm{O}}_2^ + \] .

The correct option is option C.

Note:
The mesosphere is called the ionosphere due to the presence of ions. It also contains a 5km region of non-ionised sodium. This layer weakly radiates causing a light airglow. Other metals like iron and potassium also exist in the mesosphere.