There is more than 50 times as much freshwater stored underground than in all the freshwater rivers and lakes at the surface
这句写错了,应该是;
There is more than 50 times as much freshwater stored underground as that in all the freshwater rivers and lakes at the surface
句中more than 表示超过的意思
倍数比较是as-----as 结构,第一个as 后跟比较内容,第二个比较对象,eg
his income is more than 3 times as much as mine:他的收入是我的三倍以上
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转自百度