The answer would be C. lo. No mucho, pero si lo como cuando quiero. Not much, but yes I eat it when I want.
It would not be me because the phrase "me como cuando quiero" would mean "I eat myself when I want"
It would not be te because the phrase "Te como cuando quiero" would mean "I eat you when I want" it also has inappropriate meaning.
It would also not be la because when you say "it" you are referring to helado. Helado is a masculine word, so you would use lo, a masculine pronoun in the sentence.
