Observations of the Arctic reveal that the Arctic Ocean is covered by less ice each summer than the previous summer. If this warming trend continues, within 50 years the Arctic Ocean will be ice free during the summer months. This occurrence would in itself have little or no effect on global sea levels, since the melting of ice floating in water does not affect the water level. However, serious consequences to sea levels would eventually result, because __________.
22. Which of the following most logically completes the passage?
(A) large masses of floating sea ice would continue to form in the wintertime
(B) significant changes in Arctic sea temperatures would be accompanied by changes in sea temperatures in more temperate parts of the world
(C) such a warm Arctic Ocean would trigger the melting of massive landbased glaciers in the Arctic
(D) an ice-free Arctic Ocean would support a very different ecosystem than it does presently
(E) in the spring, melting sea ice would cause more icebergs to be created and to drift south into shipping routes
To logically complete the passage’s open-ended “because,” something is needed that will explain why the continuation of the warming trend would have serious consequences for sea levels. The passage explains that the melting of the Arctic Ocean ice will not affect sea levels because the contribution that the water contained in that ice makes to sea levels is the same whether the water is frozen or liquid. But Choice C points to a way in which increasing temperatures in the Arctic could add water to the ocean, namely by melting ice on the land. So Choice C logically completes the passage and is the correct answer.
Given that the passage has already explained that melting sea ice does not affect sea levels, the formation of sea ice described in Choice A does not explain why there would be consequences for sea levels.
Choices B, D, and E all describe possible consequences of increased temperatures in the Arctic, but none of these consequences suggests a mechanism by which sea levels would change. So none of these options provides a logical completion for the passage.