C & B are switched so I'm not sure if that was a typo or not, but the answer is concentration!
I believe the answer is D
Answer:
For most of its active life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. At the end of a star's lifetime, its core becomes a stellar remnant : a white dwarf , a neutron star , or, if it is sufficiently massive, a black hole .
Explanation:
