Answer:
C. he and she
Step-by-step explanation:
In this sentence, "my father" and "my mother" are the subjects that perform the action which is "discuss". As they are the subjects of the sentence, it's necessary to use the subject forms of the pronouns: "he" and "she".
Another way to put it is by separating the original sentence in two sentences:
- He rarely discuss politics with my mother.
- She rarely discuss politics with my father.
So:
He and she rarely discuss politics.