TT4-16连接中没有，结构不太明白。。。

T-4-Q16

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.

1. though some protective measures, like the establishment of national forests and wildlife sanctuaries, having been taken decades ago, great increases in population

2. though some protective measures, such as the establishment of national forests and wildlife sanctuaries, were taken decades ago, great increases in population

3. though some protective measures, such as establishing national forests and wildlife sanctuaries having been taken decades ago, great population increases

4. with some protective measures, like establishing national forests and wildlife sanctuaries that were taken decades ago, great increases in population

5. with some protective measures, such as the establishment of national forests and wildlife sanctuaries, having been taken decades ago, great population increases

 (b)虽然用排除法选对了，但是中间那个插入语做什么成份？我觉得应该去掉were，做修饰成分才对。。晕了

though some protective measures were taken decades ago

though连接句子

呵呵，正常。。。