Is the energy released by the sun is caused by thermonuclear fusion.

Nuclear energy

Explanation:

Nuclear energy (also called atomic energy) is the energy found in the nucleus of an atom.

This energy is released spontaneously (within the stars and the sun) or artificially (in nuclear reactors built by humans) in nuclear reactions, which are divided into two types:

-Fission (separation of the components of the atom nucleous)

-Fusion (joining two light nuclei to form a heavier nucleous)

In the case of the Sun, the nuclear reactions that occur are due fusion, in which the hydrogen is converted into helium.

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .