Nuclear Fusion: in Massive Stars, Three Helium Nuclei Fuse Together

Nuclear fusion: In massive stars, three helium nuclei fuse together, forming a carbon nucleus. This reaction heats the core of the star. The net mass of the three helium nuclei must therefore be

A) higher than that of the carbon nucleus.
B) less than that of the carbon nucleus.
C) the same as that of the carbon nucleus since mass is always conserved.
D) the same as that of the carbon nucleus since energy is always conserved.