Reading test

One of the most shocking scientific realizations of all time has slowly been dawning on us: The earth's climate has great reversals every few thousand years, and with breathtaking speed. There is a good chance that we could go back to ice-age temperatures within a decade and judging from recent discoveries, a sudden cooling could be _(11)_ by our current global-warming trend. Europe's climate could become more like Siberia's. Because such a cooling would occur too _(12)_ for us to make adjustments in agricultural productivity and supply, it could fatally damage civilization as we know it. For a quarter century, global-warming theorists have warned that we need to prevent greenhouse gases from warming things up, raising the sea level, destroying habitats, and intensifying storms. Now we know and from an entirely different group of scientists exploring separate lines of reasoning that the most _(13)_ result of global warming could be a sudden cooling. We are in a warm period now. Scientists have known for some time that the previous warm period ended 117,000 years ago, with the return of cold temperatures that led to an ice age. But the ice ages aren't what they used to be. They were formerly thought to be very gradual, with both air temperature and ice sheets changing in a slow, 100,000-year cycle tied to changes in the earth's orbit around the sun. _(14)_, our current warm-up, which started about 15,000 years ago, began suddenly with the temperature rising sharply while most of the ice was still present. We now know that there's nothing "glacially slow" about temperature change: Together with the gradual, long-term cycle, there have been dozens of warnings and coolings that lasted only centuries. There seems to be no way of _(15)_ the conclusion that global climate flips occur frequently and unexpectedly.
11
(A). postponed(B). replaced(C). triggered(D). recorded
12
(A). gradually(B). often(C). rapidly (D). slowly
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(A). ideal(B). unlikely(C). beneficial(D). dangerous
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(A). Similarly(B). However(C). Therefore(D). Consequently
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(A). proving(B). forcing(C). escaping(D). suggesting