American scientists concluded that while daily exercise is most helpful, every other day, three days a week will keep a sufficient level of physical fitness. ( Passage Four)

【参考答案】

美国科学家得出了这样的结论，尽管每天进行锻炼对身体最为有利，但隔天或是一周三天进行锻炼，也足以使我们能够保持身体健康。