#1: the atomic number of an atom is equivalent to which of the following?
a. the number of protons plus the number of neutrons in the nucleus
b. the number of electrons outside the nucleus
c. the number of protons in the nucleus
d. the number of neutrons in the nucleus
***my c
is that right? ?

Yes, you are correct. The amount of protons in the nucleus is also the same as the atomic number of an element in the periodic table. If you take a look at the periodic table of elements, the sequence of the elements, let us say H or hydrogen = 1. It only means that a Hydrogen atom contains 1 proton only and so on for the next chemical element in the table. 

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).