Answer:
Mary Jean and Beth volunteered for the past five years at a local shelter for abused pets.
Explanation:
In the given sentence, the action/ verb is something that's done in the past. This is identified by the phrase "for the past five years", meaning it is an action that's been done in the past, that happened some years before the present. Therefore, the verb "volunteer" will be used on the past form "volunteered".
So, the newly revised sentence will become-
Mary Jean and Beth volunteered for the past five years at a local shelter for abused pets.
