It’s organized by the atomic number which is the protons so the answer is A although they can be organized through groups and periods if valance electrons are included
S + O₂ = SO₂
1 mole S ------------ 1 mole SO₂
? mole S ----------- 15.0 mole SO₂
S = 15.0 * 1 / 1
= 15 moles of S
hope this helps!
