37.Researchers have established that when people are mentally en-gaged， biochemical changes occur in the brain that allow it to act more effectively in cognitive （认知的） areas such as attention and memory. 研究人员证实：人们在动脑筋时，头脑会产生很多的变化，使头脑在注意力和记忆力这类认知领域中更有效地活动
38. During the ice ages ， human beings exposed to the colder temperatures of the time would often make their homes in caves. 在冰河时代，人们面临当时较为寒冷的气温，常常在洞穴里安家。
逆序法
39. It was extended and preserved in the 19th century ， when our nation spread across the continent ， saved the union， and abolished the awful scourge of slavery.在19世纪，我们的国家横跨大陆，拯救了联邦，废除了恐怖的奴隶制的蹂躏，这一信念才得以流传可扩展。
40.By January 16， just a month after the beginning of the offensive on which Hitler had staked his last reserves in men and guns and ammunition ， the German forces were back to line from which they had set out.到1 月16日，德军又回到了他们当初出击的战线，这恰好是希特勒把他最后的兵力、大炮、弹药储备孤注一掷、发动进攻的一个月之后。
41. Five score years ago， a great American ， in whose symbolic shadow we stand by，signed the Emancipation Proclamation. 100 年前，一位伟人签署了《奴隶解放宣言》，今天，我们正是站在这位伟人富有象征意义的雕象下集会。
变序法（综合法）
42. Can you answer a question which I want to ask and which is puzzling me？
我有个问题弄不懂，想请教你，你能回答吗？
43. He had cleared up those confusions which arose from different medicines that had the same name and from various names that had been given to the same substance. 药名混乱，有的由于不同药物同一名称所引起，而有的则由于同一药物不同名称所造成，他对此一一作了澄清。
44. One teacher writes that instead of drowning students‘ compositions in critical red ink ， the teacher will get far more constructive results by finding one or two things which have been done better than last time， and commenting favorably on them.一位老师这样写到：如果我们能从学生作文中找出一两处比上次做的更好的地方，并提出表扬性评语，而不是用红墨水把学生的作文批改的一塌糊涂，我们就能从中的更富有建设性的结果。
45. Ours is a profession which traditionally has been guided by a precept that transcends the virtue of uttering the truth for truth‘5 sake ， and that is as far as possible do no harm. 我们的职业传统上格守一个信条，那就是尽可能的不造成伤害，这一信条胜过为讲真话而讲真话的美德。
46. The president said at a press conference dominated by questions on yesterday election results that he could not explain why the Republicans had suffered such a widespread defeat，which in the end would deprive the Republican Patty of Tong-held superiority in the House.在一次记者招待会上，问题集中于昨天的选举结果，总统就此发了言。他说他无法解释为何共和党遭到如此大的失败。这种情况最终使共和党在众议院中失去了长期享有的优势。
为何要拆句？
47.Literature
