Answer:
A. Heat is a form of energy.
Step-by-step explanation:
The Sun emits heat, which is a form of energy. This heat energy is supplied to the Earth by the sun, when the solar energy is converted to heat energy. The study of heat energy and its conversion from one form to another is a branch of physics called THERMODYNAMICS.
Hence, a physicists will be interested in studying the heat given off by the sun because it is one of the several forms of energy.