The caterpillar of the monarch butterfly feeds on milkweed plants, whose toxins make the adult monarch poisonous to many predators. The viceroy butterfly, whose caterpillars do not feed on milkweed plants, is very similar in appearance to the monarch. Therefore, it can be considered that the viceroy is so seldom preyed on because of its visual resemblance to the monarch.
Which of the following, if it were discovered to be true, would most seriously undermine the argument?
(A) Some predators do not have a toxic reaction to insects that feed on milkweed plants.
(B) Being toxic to predators will not protect individual butterflies unless most members of the species to which such butterflies belong are similarly toxic.
(C) Some of the predators of the monarch butterfly also prey on viceroys.
(D) The viceroy butterfly is toxic to most predators.
(E) Toxic to predators is the principal means of protection for only a few butterfly species.