Question

multiple - choice question
mass number is the number of protons and neutrons within a single atom of an element and average atomic mass is the average mass of all the possible isotopes of that element.
f
t

Explanation:

The mass number of an atom is indeed the sum of protons and neutrons in a single atom of an element. The average atomic mass is calculated as the weighted - average mass of all the possible isotopes of that element, taking into account their relative abundances.

Answer:

T