Answer:
C. The mass of an electron is much less than the mass of a proton or
a neutron.
Explanation:
When we compare the mass of an electron to that of proton or neutron, the mass of an electron is much less than the mass of a proton or a neutron.
Electrons are negatively charged particles in an atom
Protons are positively charged particles
Neutrons do not carry any charges.
We can see that electrons have very small mass and this is why when calculating the mass of an atom, we use the sum of the number of protons and neutrons.