When comparing elements in the same column of the periodic table, which factor- distance or the number of protons seems to be the dominant factor?

If what we meant here is to be the dominant factor which determines the attractive forces between the outermost electron and the nucleus of an element, then the answer to this question would be:

Distance

This is because, the distance in the periodic table highly suggest the strength of the electronegativity of an element. 

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a