Self-paced
On the basis of the available evidence, Antarctica has generally been thought to have been covered by ice for at least the past 14 million years. █████████ ████████ ██████████████████████ ███████ ██ █ ████ ██████████ █████ ████ ██ ███████████ █████████ ████ ██████████ █████ ███ ███ █████ ████████ ███████ ███████████ █████ █████ ███████ █████ ████ ██████████ ███ █████████ ███ █████ ████ ███████████ ████ ███████ █████ ████ ██████ ██████ ████████ ███████ ██ ████████ ████████ ██ ████████████ █████████ █████ ████ ██████ ███ ███ ██████ ████ ███████ ███ ██████ ███ ██████████ ███ ██████████
Stimulus Summary
For a long time, scientists thought Antarctica had been ice-covered for at least 14 million years. Then they found three-million-year-old fossils under the ice in central Antarctica, of a kind that had only ever shown up in ocean-floor sediments before. The author concludes that the ice sheet must have briefly melted about three million years ago.
The thinking goes: these fossils have only been seen in ocean-floor mud, so central Antarctica must once have been ocean floor, which means the ice melted and the sea rose high enough to submerge the continent. The "after all" sentence backs this up by naming two things that could have melted the ice, severe warming or volcanic activity.
The author assumes the only way these fossils could be there is if the spot had been ocean floor, ignoring other ways they might have arrived. And the support only says warming or volcanic activity could have melted the ice, which shows melting was possible, not that it actually happened.
16.
Which one of the following ██ ███ ████ ██████████ ██ ███ █████████
a
Antarctica is no ██████ █████████ ███████ ██ ████ ████ ███████ ██ ███ ███ ███ ████ ██ ███████ ██████
This is about what people generally believe, which the conclusion does not make a claim about. The author argues that the ice melted three million years ago, but never says others agree with that view. The author could be alone in it, standing apart from the general opinion.
b
It is not ███ ████ ████ ███████ ███████ ██ ███ ████ ████████ █████ ██ ██████████ ███ █████ ████ ██ ███████████ ██████████
This is not the conclusion, and it is not even something the author is committed to. The main point has to be about the ice melting, and (B) is about where these fossils can be found.
c
The ice sheet ████████ ██████████ ███ ███ ████ ████████████ ███████ ██████████ ███ ████ ██ ███████ ██████
This best restates the conclusion, even though the wording might throw you off. You may expect the answer to mention three million years, and instead (C) talks about the past 14 million years. That number is fine here, because the author's conclusion is a rejection of the opening view that ice covered Antarctica continuously for those 14 million years. Saying the ice melted three million years ago is just another way of saying it was not present without a break across that whole stretch, which is what (C) captures.
d
What caused Antarctica ██ ██ █████████ █████ ███ ███ ███ ███ ███████ ██ ███ ███ █████ ████ ███ ██████████ ███████ ███ ██████████
(D) recasts the point as an explanation of what caused Antarctica to be submerged, but the author's conclusion is about timing, that the ice melted at a specific point within the supposed 14-million-year freeze.
e
The ice sheet ████████ ██████████ ███ ██████ ██████ ██ █ ██████ ██ ████████ ████████ ██ ████████████ █████████ ██ ██ █ ██████ ██ ██████ ████████ ████████
This is the support introduced by "after all," not the conclusion. Naming volcanic activity and severe climatic warming as things that could have melted the ice is offered to make the melting claim believable. (E) also overstates that support: the stimulus only says these two things could have melted the ice, not that one of them actually did or that they were the only possibilities.