Above the tree line there is a zone that is generally called alpine tundra.
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 linchens and some prostrate cushion plants. 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.
@@@ At this great height, rocks, warmed by the sun, melt small snowdrifts. @@@
要插入的句子
This explains how, for example, alpine cushion plants have been found growing
at an altitide of 6,180 meters.
两个@@@都是选项
一个是正确答案 一个是我的错误选择
正确答案是后者
我选了前者
请问是否有高人可解答?
感谢~~

关键字explain, 所以前一句要是因, The highest那句无法

我不太懂为什么融雪可以解释他的生长因为这样才有水源?

是的。插入句里有This, 一定是前面有说过的事情才会用this代替，所以插入句前面应该要有可以放在 this 这个位置的东西，而 this 代替的something 要能够 explain (解释) 为什么alpine cushion 这种植物可以在很高的地方生长。你的第一个@@@前一句只说明了发现有植物生长的最高高度是喜马拉雅山上6100公尺的地方而已，所以放这里并不通顺。最后一句说了在这高度的石头因为会被阳光加热，所以会融化少量降雪，而这件事才可以解释植物可以在那么高的地方生长。(融雪＝有水，是这样子没错！）

好的 超清楚的解释....感谢你