This is consistent with the author’s interpretation. We already know tiger salamander larvae are “plagued by a deadly bacterium.” The author never assumes that the bacterium infects mainly cannibalistic tadpoles. So pointing out that many non-cannibals are infected has no impact on the author’s argument.

The author’s discussion of the tiger salamander doesn’t require any belief about what causes some larvae to be carnivores and some to be omnivores. We’re simply examining the behavior of carnivores — why do they avoid eating kin? What causes the carnivores to be carnivores doesn’t impact the reasoning.

This undermines the author’s interpretation in the last sentence by providing another potential explanation for the carnivorous tiger salamanders’ behavior. Maybe they avoid eating kin because it’s a way to help increase the chances their own offspring survive. If so, the tiger salamanders aren’t necessarily trying to preserve their “own life” — they’re still concerned about their relatives. (One’s offspring are part of one’s relatives.)

This doesn’t undermine the author’s reasoning, which is based only on the behavior of cannibal tiger salamanders. Whether noncannibals produce more or fewer offspring doesn’t suggest any explanation for why cannibals avoid eating their kin or otherwise suggest the author’s interpretation might be wrong.

This doesn’t undermine the author’s reasoning, which is based only on the behavior of cannibal tiger salamanders. Whether cannibals are immune to some diseases that noncannibals are not doesn’t suggest any explanation for why cannibals avoid eating their own kin. (E) might be tempting if you assume that the cannibals are immune to the bacterium described, but we have no reason to think that’s true.