Attached is a periodic table that shows how electronegativity varies along the groups and lines. It is not the graph but the purpose id the same.
Electronegativity is the attraction that an atom exercises over the electrons in a chemical bond with another element. As we can see in the attached table, electronegativity increases from the first group to the last and from the bottom line to the top line. So, the correct answer would be "elements of group 1".
