Question

the mass number indicates the number of ______ in an atom.

a. protons
b. electrons
c. neutrons
d. protons and neutrons

Explanation:

The mass number of an atom is the sum of the number of protons and neutrons in its nucleus. Protons and neutrons are located in the nucleus and contribute to the mass of the atom. Electrons have a negligible mass compared to protons and neutrons and do not contribute significantly to the mass number.

Answer:

D. protons and neutrons