How are the number of protons represented on the periodic table

a. atomic mass

b. isotope

c. atomic number

d. mass number

Option C, Atomic number

Explanation:

All element are arranged in a periodic table as per their atomic number. While moving across each group of periodic table from left to right, one can see that atomic number increases towards the right end of  each group.

An atomic number is nothing but the number of protons in the nucleus of an element. Thus , indirectly it is the proton number that defines the position of an element in a periodic table.

Hence, option C is correct.

"a.) well–developed vascular system."