Look at the four letters (A,B,C,D) that indicate where the following sentence can be added to following passage.

This explains how, for example, alpine cushion plants have been found growing at an altitude of 6,180 meters.

Where does the sentence fit?

Above the tree line there is zone that is generally called alpine tundra. A Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants. B Some plants can even survive in favorable microhabitats above the snow line. The highest plants in the world occur at around 6,100 meters on Makalu in the Himalayas. C At this great height, rocks, warmed by the sun, melt small snowdrifts. D

The answer is D, but I see that the choice C is also make sense. Could you please help me with this problem? Thank you so much!

closed as off-topic by FumbleFingers, user66974, choster, anongoodnurse, RyeɃreḁd May 23 '14 at 16:39

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  • 1
    The final sentence gives [one] reason why plants can exist at such great heights (the availability of usable water); it would not make sense to insert 'This explains ...' before the reason. (But I'm not sure that we're supposed to address chunks larger than individual sentences here.) – Edwin Ashworth May 22 '14 at 6:46
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    This question appears to be off-topic because it is about logical reasoning and the relationship between cause and effect, not the English language – FumbleFingers May 23 '14 at 10:50

The reason D might be considered the best answer is because the fact "rocks melt small snowdrifts" is the explanation for how plants are able to grow at that height.

Before location D, there is no given explanation for how, which the target sentence needs to refer to and build on. There are only statements equivalent or similar to "some plants grow at high altitudes", even right before location C.

  • I cannot vote for your answer. Thank you so much @bluebaby – user52523 May 23 '14 at 8:23

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