No clue how to explain this. Just don't understand it:

Question

Which formation of the monatomic ion of oxygen is the most energetically favorable?
A) O2-
B) O2+
C) O4+
D) O-
E)O6+

Answer 1

the formation of which monatomic ion oxygen is the most energetically favorable

Answer 2

o2-

Answer 3

02-

Answer 4

O2-