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南极是地球上最不宜居（inhospitable）的地方。然而自从20世纪早期以来，季节性融雪（seasonal melting）形成的短期河流和湖泊打破冰雪世界单调的面貌（break up the monotonous line of ice），给白茫茫的大地带来了生机。这些水体并不像科学家以前想的那样少见。上周四发表的研究报告显示，南极边缘（fringes）存在范围极广数量巨大的融水水系。有些融水河流长达75英里，有些水体高于海平面4300英尺，而之前科学界的共识是这个高度是不可能存在液体水的（liquid water had been thought impossible）。科学家认为水系的生长和扩张与过去几十年温室气体的加速排放脱不了干系，而且如果人类一如既往（business as usual）地忽视全球变暖，那么南极冰架表面会出现越来越多的液体水，大块浮冰将破碎入海，各大洲的沿海土地都将沉没。

今天的句子：

The extent of the drainage network has led some to worry that the meltwater may help weaken ice shelves in the Antarctic that are already hanging on by a thread, causing large chunks of ice to break off and contribute to rising sea levels.

词汇突破：

1.Extent 范围；程度

2.Drainage network 水系

3.Meltwater 融水

4.Ice shelf 冰架

5.Antarctic 南极

6.Chunk 大块

7.hanging on by a thread 命悬一线

确定主干：

The extent of the drainage network has led some to worry that…

切分成分+独立成句：

1.The meltwater may help weaken ice shelves in the Antarctic 宾语从句

2.that are already hanging on by a thread

That= ice shelves (因为后面的动词是are)

Ice shelves are already hanging on by a thread  

3.causing large chunks of ice to break off and contribute to rising sea levels

= the meltwater cause large chunks of ice to break off and contribute to rising sea levels

参考译文：水系的范围使一些人担心融水可能会削弱南极的冰架，这些冰架本就“命悬一线”，而且融水令大块大块的冰破裂并引发海平面的上升。

明天的句子：

When new symptoms pop up, the temptation to switch medications can be hard to resist, especially because a complex prescription history can condition families to look to drugs first. But sometimes the solution is far simpler.

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