I attended the answer. I hope this helps you.
Since each Chlorine molecule is -1 and wants to gain an electron, 2 Chlorine atoms like to come together to form Cl2 by sharing 2 electrons each to form a single bond between the 2 atoms. Since both Chlornine has the same electronegativity, the bond is non-polar covalent since there electrons are evenly shared.
I think it’s 2.45, not 100% sure
A is your answer.
On the periodic table the atomic number is the number of protons inside the nucleus.
Phosphorus + Sulfur ------> Phosphorus sulfide
2P + 3S ------> P2S3
Hope it helped!