1． This development-and its strong implications for US politics and economy in years ahead-has enthroned the South as America's most densely populated region for the first time in the history of the nation's head counting.
　　【译文】这一发展--以及其对今后几年美国政治和经济的强大影响--在美国人口普查史上第一次确定南部是人口最密集的地区。

　　【析句】句子的主干是This development... has enthroned the South as America's most densely populated region。破折号之间成分是对主语的补充。for the first time in the history是全句的状语。

　　【讲词】enthrone意为“登基；加冕”，在句中的意思是“正式确定为”或“成为”。"Ten years ago I was enthroned as the reincarnation of the 10th Panchen Lama," the 11th Panchen Lama told the crowd.（十一世班禅告诉人群：“十年前我被正式确定为第十世班禅的转世灵童。”）
　　head counting是census（人口普查）的通俗说法。

　　2．Often they choose-and still are choosing-somewhat colder climates such as Oregon, Idaho and Alaska in order to escape smog, rime and other plagues of urbanization in the Golden State.
　　【译文】他们常常选择--现在依然这样选择--一些气候较冷的地区，如俄勒冈、爱达荷和阿拉斯加，为的是躲开"金州"（加利福尼亚）的烟雾、犯罪和其他在城市化进程中出现的问题。

　　【析句】这是一个单句，其主干结构为They choose... and are choosing colder climates。破折号之间的成分是补充谓语成分。such as Oregon,Idaho and Alaska是 somewhat colder climates的同位语，注意climates在句中并不是“气候”的意思，而是指“地区”。in order to escape smog,crime and other plagues of urbanization in the Golden State作目的。

　　【讲词】 plague作名词时表示“瘟疫；麻烦；苦恼；灾祸”，作动词时意为“折磨；使苦恼；使得灾祸”。Health officials feared a dread plague was in the making.（卫生官员担心一种可怕的瘟疫正在形成。）Could the bird flu be the plague of our century?（禽流感会成为我们这个世纪的瘟疫吗？）For years, the country has been plagued by violence.（多年来这个国家一直受到暴力的困扰。）