Gravity pushes against all objects, trying to crush it. What pushes against gravity in: a main sequence star, a white dwarf, a neutron star, and a black hole?

heat pressure, neutron degeneracy, electron degeneracy,nothing.

Explanation:

In main sequence star, gravity's inward pull is greatly balanced by the heat pressure. In the white dwarf, gravity is mainly balanced by the electron degeneracy pressure that arises from the fact that the electrons are fermions and they obey the Pauli's exclusion principle.  So there is no two electrons that have the same the four quantum numbers.

While in neutron star, the neutron degeneracy pressure obeys the Pauli's exclusion principle that gives rise to the degeneracy pressure and noting pushes against the gravity in the black hole. Therefore the correct option is the heat pressure, neutron degeneracy, electron degeneracy and nothing.