Final answer:
The two balanced forces in a main sequence star are gravitational force and electromagnetic force, providing stability.
Step-by-step explanation:
The correct answer to the question is A) Gravitational force and electromagnetic force.
In a main sequence star, the two forces that are balanced and make it stable are the gravitational force and the electromagnetic force.
The gravitational force is responsible for pulling the matter in the star towards its center, creating a compressive force that tries to collapse the star. On the other hand, the electromagnetic force, specifically the electromagnetic radiation, produced by the nuclear fusion reactions in the core of the star, creates an outward pressure that counteracts the gravitational force. This pressure is known as thermal pressure.
These two forces, the inward gravitational force and the outward electromagnetic force, balance each other, preventing the star from collapsing or expanding, and maintaining its stable state as a main sequence star.