The stomach and intestines of the pot-bellied pig adapt to new foods more quickly than any other animal ever studied, thus enabling it to eat a broad diet that may include manure, insects and grubs, and household trash without inducing gastrointestinal distress.
(A) The stomach and intestines of the pot-bellied pig adapt to new foods more quickly than any other animal ever studied, thus enabling it - The original sentence compares "stomach of the pot-bellied pig" with "any other animal". Wrong comparison. Pigs must be compared with other animals, and stomach of pig with stomach of other animal Eliminate
(B) Because the stomach and intestines of the pot-bellied pig adapt to new foods more quickly than do those of any other animal ever studied, it enables them - the issue here is "it" because it has no clear antecedent. "It" cannot refer to "pig" because pig does not enable stomach and intestines to eat a broad diet. Instead, we need "they", stomach and intestines, enable "it", pig, to eat. Option B uses these pronouns the other way around Eliminate
(C) Because they adapt to new foods more quickly than any other animal ever studied, the stomach and intestines of the pot-bellied pig enable it - This option compares "the stomach and intestines" (they - pronoun "they" in subordinate clause, "because", refer to main subject of main clause) to "any other animal". Wrong comparison. We either compare "pig" to "other animal" OR "stomach and intestines of pig" to "stomach and intensities of other animal" Eliminate
(D) The stomach and intestines of the pot-bellied pig adapt to new foods more quickly than does any other animal ever studied, enabling them - Couple of issues here. First, this option again compares "stomach and intestines" to "any other animal" - wrong comparison. Second, "them" seems to refer to "stomach and intestines" as if "stomach and intestines" eat a broad diet. Although, stomach and diet certainly are related, we still do not say stomach eat since stomach does not perform the action per se (action: eat). For whatever reason, we can eliminate D
(E) The stomach and intestines of the pot-bellied pig adapt to new foods more quickly than do those of any other animal ever studied, enabling it - This is out best answer so far. "stomach and intestines" of pig is compared to stomach and intestines [those] of other animal. "It" correctly refers to pig as it is the pig that eats the broad diet.
E is best answer