What happens to the density of the core of a high-mass star as it collapses?

It starts to collapse under its own gravity. Stars which are massive enough start to crush the protons and electrons to form neutrons. These form a huge star-sized atomic nucleus, basically just neutrons, a neutron star is. A normal star can collapse into a neutron star.
.
i hope this helps a little
.
zane

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.