有问题请教!谢谢!

icecreamr

1:Humans have been damaging the environment for centuries by overcutting trees and farming too intensively, and   (though some protective measures, like the establishment of national forests and wildlife sanctuaries, having been taken decades ago, great increases in population )  and in the intensity of industrialization are causing a worldwide ecological crisis.
(A) though some protective measures, like the establishment of national forests and wildlife sanctuaries, having been taken decades ago, great increases in population
(B) though some protective measures, such as the establishment of national forests and wildlife sanctuaries, were taken decades ago, great increases in population
(C) though some protective measures, such as establishing national forests and wildlife sanctuaries having been taken decades ago, great population increases
(D) with some protective measures, like establishing national forests and wildlife sanctuaries that were taken decades ago, great increases in population
(E) with some protective measures, such as the establishment of national forests and wildlife sanctuaries, having been taken decades ago, great population increases

答案是 B
我不知道" increase" 在此是起什么作用?

2:For protection from the summer sun, the Mojave lived in open-sided, flat-topped dwellings known as shades, each a roof of poles and arrowweed supported by posts set in a rectangle.
(A) each a roof of poles and arrowweed
(B) each a roof of poles and arrowweed that are being
(C) with each being a roof of poles and arrowweed
(D) with roofs of poles and arrowweed to be
(E) with roofs of poles and arrowweed that are

答案是 A
能讲讲" each" 得用法吗?

非常感谢!

gemj

作主语：
great increases ... are causing a worldwide ecological crisis.