Answer:
a). The sum of the masses of the u, u, and d quarks that make up the proton.
Step-by-step explanation:
The proton has smaller particles like quarks and gluons. However, the gluons have no mass, so a portion of the proton mass is the mass of the quarks. Therefore, the mass of a proton is due to
a) The sum of the masses of the u, u, and d quarks that make up the proton.