018. Until quite recently, American presidents lived in a world in which the public and private realms of their lives were largely separate, in which the press cooperated in maintaining the distinction, and in which Americans judged national leaders without receiving, or expecting, intimate information about them.
=Until quite recently, American presidents/ lived in a world/ in which the public and private realms of their lives/ were largely separate/, in which the press/ cooperated/ in maintaining the distinction/, and in which Americans/ judged national leaders/ without receiving, or expecting, intimate information about them.
#直到 近为止，美国总统/一直生活在这样一个世界里/在那里他们生活的公共和私人领域被大大的分开了/，。
*这句话虽然很长，但不难理解，都在说美国总统生活在什么样的世界。唯一一个难点是 Until 的理解。在这句话中用了 live 这个动词，根据 Until 的使用规则，如果后面接的是延续性动词，如 live，则表达动作一直进行，直到 Until 后的的时间为止。所以，句子的意思是美国总统以前一直生活在这样的世界中，而 近他们不在生活在这样的世界里了。
019.Intended primarily to stimulate family summer travel, the new airfare, which allows both an adult and a child to fly for the price of one ticket, also shortens the advance-purchase requirement for family travel to a minimum of seven days rather than
fourteen.
=Intended primarily to stimulate family summer travel/, the new airfare/, which allows both an adult and a child to fly for the price of one ticket/, also shortens/ the advance-purchase requirement for family travel/ to a minimum of seven days rather than fourteen.
#主要为了刺激家庭暑期旅游/新的飞机票价/允许一个成人和一个孩子乘坐飞机只花一张票的钱/同时缩短家庭旅游预付要求/到 短 7 天而不是 14 天。
*句子比较简单容易理解。注意一些连接句子的短语：Intended to，rather than 等。
020. New techniques in thermal-scanning photography, a process that records radiation from surface areas, have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river.
=New techniques in thermal-scanning photography/, a process/ that records radiation from surface areas/, have made it possible/ to study in greater detail than ever before/ the effects of calefaction, or warming, of a river.
#新技术在终端扫描摄相方面/(就是)一个过程/记录表面区域的辐射/使变成可能/比以前更细微的研究/河流 calefaction 或变暖的结果。
*这个句子比较读起来有点别扭，原因是 of 短语和 made it possible 使得中英文语序不同。至于 calefaction，属于认识就反映不认识就过去的词类，况且翻成中文恐怕绝大多数读者还是不知其所以然。