Although most species of nondomestic mammals in Australia are marsupials, over 100 species—including seals, bats, and mice—are not marsupials but placentals. It is clear, however, that
these placentals are not native to this island continent:
all nonhuman placentals except the dingo, a dog introduced by the first humans that settled Australia,
are animals whose ancestors could swim long distances, fly, or float on driftwood.
The conclusion above is properly drawn if which one of the following is assumed?
Blue text is the conclusion. Dark blue is provided more details as support to the conclusion.(A) Some marsupials now found in Australia might not be native to that continent, but rather might have been introduced to Australia by some other means. - WRONG. Irrelevant. Need to place importance to placentals more than marsupials.
(B) Humans who settled Australia probably introduced many of the placental mammal species now present on that Continent. - WRONG. Open so much that it can go in either direction.
(C) The
only Australian placentals that could be native to Australia would be animals whose ancestors could not have reached Australia from elsewhere. - CORRECT. Strikes right cords. Does the opposite of what the support to conclusion did - kind of an exception discussed.
(D) No marsupials now found in Australia can swim long distances, fly, or float on driftwood. - WRONG. Like A, this is irrelevant.
(E) Seals, bats, and mice are typically found only in areas where there are no native marsupials. - WRONG. Again irrelevant.
Answer C.