The author is only arguing that the comet theory is plausible; the fact that other theories differ from the comet theory doesn’t weaken the argument. It doesn’t weaken our argument that other plausible explanations may exist.

(B) suggests that the extinction of the dinosaurs was driven by some factor that differentiated dinosaurs from other animals with similar habitat and climate needs. If the comet theory was true, animals with similar physiology and habitat to dinosaurs would have gone extinct too.

(C) just says that one specific kind of evidence cannot be used. The inability to use skeletons as evidence does not weaken the argument that the comet theory is plausible. (C) makes the inappropriate assumption that skeletons are the only source of information available.

(D) is too broad. The animal species referenced in (D) could have had vastly different requirements for habitat and climate. It makes sense that some animals survived the incident that killed the dinosaurs.

The argument that the comet theory is plausible doesn’t require a full understanding of the impacts of a comet collision on plants and animals, so (E) does not impact the argument.