As a White Dwarf Cools, Its Radius Remains the Same

As a white dwarf cools, its radius remains the same. Why is this?

A) because pressure due to nuclear reactions in a shell just below the surface keeps it from collapsing
B) because pressure does not depend on temperature for a white dwarf, since the electrons are degenerate
C) because pressure does not depend on temperature, since the star has exhausted all its nuclear fuels
D) because material accreting onto it from a companion maintains a constant radius