The answer is b. fluorine (F). This is because fluorine is a more electronegative (electron loving) atom compared to oxygen. It is found on the 7th group of the periodic table, so it has 7 valence electrons. It only needs one more electron to achieve the ideal number of valence electrons which is 8. Oxygen, on the other hand, is in group 6 so it needs 2 more electrons to complete its valency. Helium can't be the answer because it is already in group 8, meaning it is already stable and won't release energy.
