今天环球教育小编主要向大家讲解托福写作中三个必备的连接词：by comparison、by contrast和therefore。虽然是必备之词，但同学们也不要用错哦。
By comparison
　　1) He was mortified by comparisons between his classmates’ good marks and his own.拿自己的成绩与同学们的优异成绩相比较他感到羞愧。
　　2) By comparison, expenditure on education increased last year.相比之下，去年教育经费增加了。
　　By contrast
　　1) By contrast, she was much more outspoken.对比起来，她坦率得多。
　　2) When you look at their new system, ours seems very old-fashioned by contrast.看看他们的新系统，我们的相比之下就显得太过时了。
　　Therefore
　　1) He is young and therefore easily pervertible.他年轻，因而容易变坏。
　　2) All sincere opinions should therefore be respected.因此一切诚恳的意见都应该收到尊重。
　　3) He is highly strung, and therefore, subject to heart attacks.他神经高度紧张，所以很容易发心脏病。
　　4) Therefore energy is now not a peripheral but a central issue in the economy.因此，能源在现时经济中并非枝节问题而是一个中心问题。
　　5) We have a growing population and therefore we need more and more food.我们的人口越来越多，因此我们需要越来越多的食物。