The main components of the mesosphere are:

The mesosphere exists just above the stratosphere and the troposphere. It starts about 50km from the surface of the earth and continues up to 120km. In this region, temperatures drop as they rise.
The upper part of the mesosphere is also known as the ionosphere. During the day, in this phase ionization occurs when nitric oxide is degraded by Lyman series alpha hydrogen radiation. Ionization is also weak during the night, free electron and ion combine again forming a neutral mixture.

So, we can conclude that the main components of the mesosphere are${\mathrm{NO}}^{+} \mathrm{and} {{\mathrm{O}}_2}^{+}$.

Hence, the correct option is C.