作者：英吉
21.
When Nigeria achieved full independence in 1960, they had already established a federal political structure consisting of three regions based on the three major population clusters that were in its borders.
(A) they had already established a federal political structure consisting of three regions based on the three major population clusters that were in.
(B) they already had established a federal political structure consisting of three regions that was based on the three major population clusters inside.
(C) they already had established a federal political structure that consisted of three regions based on the three major population clusters in.
(D) it had already established a federal political structure that consisted of three regions based on the three major population clusters within.
(E) it already had established a federal political structure consisting of three regions being based on the three major population clusters it had within.
原文大致意思：当尼日利亚完全独立的时候，这个国家已经建立了一个政治structure，这个structure是由三个regions构成的，而这三个regions（后面实在是看不懂了）
题目分析：根据划线外提示，Nigeria是一个国家，后面不能用they，我们可以很快把A B C杀掉，DE进行比较，第一个区别就是already位置不一样，这个区别不大，不管，第二个区别就是一个用that consisted of 一个用consisting of，读起来意思也差不多，不管，划线最后部分一个用了it一个没有，这个it显然指尼日利亚,但是划线外已经说了its borders了，不用再化纤内再说一遍了，画蛇添足，选D。
