The correct option is:
Reactivity decreases down a group, and electronegativity increases down a group.
In general, for nonmetals, reactivity tends to decrease as you move down a group in the periodic table. This is because the additional electron shells increase the distance between the nucleus and the valence electrons, making it harder for the atom to attract additional electrons (which is related to electronegativity). Electronegativity, on the other hand, generally increases as you move up a group because the atoms are smaller and more effective at attracting electrons.