D. All I can say about my rival's idea is that he's a thief and he should be ignored.
Explanation:
Ad Hominem is a Latin word that means "against the man".
This particular fallacy of ad hominem is simply the act of going against sound logic when making an argument to make personal attacks on the speaker.
From the example above, there was a personal attack on the rival against his idea while bringing up the matter that he was a thief and should be ignored.
This is a very good example of Ad Hominem fallacy because he threw away sound logic while making his argument and instead chose personal attacks against his rival to score cheap points.
