Word Pairs


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The words
Scientists say there could be something under frozen ground that [contents / contains] many deadly diseases. Ancient microbes have [been / being] trapped for millennia in the permafrost that covers large [arenas / areas] of Earth. Permafrost is [ground / aground] that stays completely frozen for at [least / last] two years. It is common high in mountains and [nearly / near] the North and South Poles. The scientists say the permafrost is [molten / melting] because of climate change. The result could be the release of unknown, harmful viruses, which scientists are [calling / called] 'Factor X'. Birgitta Evengard, a professor in [infectiously / infectious] diseases at a university in Sweden, said we know little about Factor X and the biological [dangerous / dangers] trapped in Earth's permafrost.

Virologist Jean-Michel Claverie says there are viruses [deeply / deep] in the permafrost that are more than 50,000 years old. He said [these / them] could be harmful to [humans / humane] . Professor Claverie said "ancient viruses up to a million years old" would be the most [terrific / terrifying] because they are unknown and we have never [counted / encountered] them before. He added that [deadly / dead] bacterial diseases like smallpox and anthrax could be released [in / on] a large scale. Factor X could pose even bigger problems. However, many scientists agree that a [biggest / bigger] danger from melting permafrost is the release [on / of] methane. This is a greenhouse gas that is 80 times more [harmful / harmed] than CO2.

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