Answer: Electron has almost no mass.
Step-by-step explanation:
Mass is defined as the actual matter that is contained in a substance. At an atomic level, it is expressed in atomic mass units.
The given options are the 3 subatomic particles.
Mass of the given subatomic particles are:
Proton = 1.007276u
Neutron = 1.008664u
Electron = 0.0005485u
Mass of neutron is slightly more than the mass of proton.
From the above information, it is visible that electron has a negligible mass.
Hence, the correct answer is electron.