The mesosphere is one of the layers of Earth’s atmosphere.

The correct option is Atmosphere.

Step-by-Step Explanation:

Earth's system is broadly divided into four major spheres based on their components:
1. Atmosphere: The gaseous envelope surrounding Earth. It is divided into five principal layers according to temperature gradients:
- Troposphere: The lowest layer, where weather occurs.
- Stratosphere: Contains the ozone layer.
- Mesosphere: The middle layer located between the stratosphere and the thermosphere, extending from about 50 to 85 kilometers above Earth's surface.
- Thermosphere: Characterized by high temperatures and ionization.
- Exosphere: The outermost boundary transitioning into outer space.
2. Biosphere: The global zone containing all living organisms.
3. Hydrosphere: All of Earth's water, including oceans, lakes, ice caps, and vapor.
4. Lithosphere: The rigid outer portion of Earth, comprising the crust and upper mantle.

Since the mesosphere is a gaseous layer surrounding the planet, it is one of the layers of Earth's Atmosphere.