Final answer:
Pressure and gravity balance to maintain the shape of a star.
Step-by-step explanation:
The two things that balance to maintain the shape of a star are pressure and gravity.
Gravity pulls the matter inward, creating a force that wants to collapse the star. However, pressure generated by the nuclear fusion reactions happening in the star's core pushes outward, counteracting the force of gravity and preventing the collapse. This balance between the inward pull of gravity and the outward push of pressure maintains the shape of the star.
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