should意为应该，它的同义词组有ought to，be supposed to。ought to一般用于阅读中，用法普遍。be supposed to是比较正式的说法，书面语较多。
You ought to scrap the old bike and buy a new one.
你应该扔掉这辆旧自行车，买一辆新的。
I think I ought to get back to work.
我想我该回去工作了。
Perhaps we ought to have trusted people more
也许我们本当对人多一些信任的。