Answer:
Dependent on the element that reacted with carbon
Step-by-step explanation:
Nuclear fusion is the combination of small atomic nuclei into larger ones usually accompanied with the release of a large amount of energy.
From the problem stated, carbon fuses with another atom. The combined atom would have more nuclear particles in terms of protons and neutrons than the combining atoms. This will eventually make it weigh more than carbon and the atom it combines with. The resulting weight will depend on the combining atoms eventually.