求助天山4-16，没有问过的！

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.

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 Answer:

答案是C，相比下也没有别的了。但是我的疑问是C的结构是句子1 （Humans have been damaging the environment for centuries by overcutting trees and farming too intensively） ，and though 句子2（and though some protective measures, such as the establishment of national forests and wildlife sanctuaries, were taken decades ago），句子3(great increases in population and in the intensity of industrialization are causing a worldwide ecological crisis. )；那句子2和句子3之间的连词呢？

唯一的解释是and though中的though做连词（though也可以做副词）来连接句子2和句子3，and 用来连接句子1和句子2。 但是2个连词一起使用我还没有见过。还是我的这套分析有误，应该是别的解释！希望大家解释一下喽。