The mass number of an element is the sum of the number of protons plus neutrons.
Answer: Option C
Step-by-step explanation:
The element's mass number refers to the summative number of neutron and proton in the nucleus. In the nucleus there is the total number of protons and neutron, summed together to form the atomic mass.
Atomic mass is similar as the mass number in representation. Therefore, we have the following formula for the mass number,
Mass number of an element=Number of protons+Number of neutrons