1.Some philosophers argue that rights exist only within a social contract, as part of an exchange of duties and entitlements.

翻译：有些哲学家论证说，权利只存在在于社会契约中，是责任与权益相交换的一部分。

析句：Some philosophers argue是句子的主干，宾语是一个从句，介词短语as part of an exchange of duties and entitlements是rights的后置定语。

讲词：social contract意为“社会契约”，也可译为“民约论”或“社会契约论”，指社会成员之间或政府与人民之间确定和限制各自权利和义务的协议。

 duty意为“义务，职责”，与obligation和responsibility同义。obligation通常指特定原因而产生的具体限制，responsibility强调履行义务，duty指出于道德或伦理的考虑而受到的限制。

entitle的基本意思是“给……题名,给……称号;给予……权利; 使……有资格(做某事)”。

I think she is entitled to praise.(我看她值得赞扬。)

The book is entitled Natural Cancer Treatments.(这本书的名称是《癌症自然疗法》。)

The civil servants in our country are entitled to free medical care.(我们国家的公务员(微博)享受免费医疗。)而entitlements意为“权利”。

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 plaguesof urbanization in the Golden State.

翻译：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。）

3. 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.

翻译：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。