三个都可用虚拟语气,should可省略,但in case的从句还可以是陈述语气.Here's a stick in case you should need it.给你根木棍,也许你用得着它.《简明英汉词典》Take your skates in case you decide to go skating.把...lestfor fear that是必须引导should +动词原形吗？谢谢！是的。