请教几题---TOEFL高分语法

As he focus changed, the love poetry that Edna St.Vincent Millay produced in 1920's increasing gave way to poetry dealing with social injustice.

答案：increasing---increasingly

对这句话的意思和结构都有点不太明白，为什么1920后面加's，能不能解释一下，谢谢

For thousands of years,people have used some kind of refrigeration cooling beverages and preserve edibles.

答案：cooling---to cool  但是，kind 不应该是kinds 吗？

The world's deepest cave, Pierre St.Martin in the Pyrenees mountains,is almost three times as deep as the Empire State Building is high.

is high 是不是不对？

It has been reported that during any twenty-four hour period,a minimal of three hundered North American women start their own businesses.

答案：a minimal of -----a minimum of    但是，hour 为什么不加S？

谢谢

还有一题：

Although ferns lack flowers, they do have leaves, stems,and root.

答案：root---roots,不明白为什么要加个do？do在这里起什么作用？

2，use sth to do sth

不是use sth doing,你见过这样的表达吗？

3，对的呀，比较2个物体的不同方面

4，hour period 连着

5，do 你可以去掉它，它的作用是加强语气

as deep as第2个as 是连词，加句子。

You are as tall as Tom is tall.

因为比较对象的同一个特征，所以->You are as tall as Tom

你的句子是Tom is as tall as that lake is deep

所以不能省