disproportionation is a type of redox reaction in which an element can undergo both oxidation and reduction.
Let's take a look at the choices:
First we have the oxide ion. Oxide ion has a charge of -2 which is the lowest charge that an oxygen atom can have. Therefore, an oxide ion cannot be further reduced, so this choice is not correct.
Next we have the peroxide ion. The oxygen has a charge of -1 which means it can be further reduced. So, this choice is acceptable
Last but not least, we have the superoxide ion. The oxygen has a charge of -1/2 which means it can be further reduced. So, this choice is also acceptable.
Based on this, we have two accepted choices which are b and c.
