Final answer:
The Chandrasekhar limit is the maximum mass (approximately 1.4 Msun) a white dwarf star can have without collapsing into a neutron star, due to the degeneracy pressure exerted by electrons.
Step-by-step explanation:
The Chandrasekhar limit is the upper limit to the mass of a white dwarf, which is calculated to be about 1.4 times the mass of our Sun (1.4 Msun). Beyond this limit, the white dwarf cannot remain stable and will collapse under its own gravity.
Due to the principles of quantum mechanics, specifically the Pauli exclusion principle, there is a degeneracy pressure exerted by electrons that prevents further compression, known as degenerate gas. This degenerate pressure is what supports a white dwarf against its own gravity, but only up to the Chandrasekhar limit. If a star's core has a mass exceeding this limit after shedding its outer layers, it will continue to collapse into a neutron star, and possibly, if massive enough, into a black hole.
Thus, the correct answer to the student's question is A) The maximum mass a white dwarf can have without collapsing into a neutron star.