all work and no play makes jack a dull boy 为什么make加s?

由and/both...and连接的并列结构作主语，可根据主语的意义决定谓语动词的单、复数形式。 例如： Pancakes and syrup is a tasty breakfast. The number and diversity of British newspaper is considerable. Good and bad taste are inculcated by example. Fish and chips are getting very expensive. A truck and a car were in the ditch. Both Cathy and her daughter Lida have gone fishing in Canada.