lest
1.lest所引导的从句里通常用should，如He hid it lest she should see it和He will hide it lest she should see it。不用should而用虚拟现在式，现在主要流行在美国，如He hid it lest she see it和He will hide it lest she see it。不用should而用shall，may或might的也有，但很不普通。不用should而用陈述现在式或陈述过去式的也有，如He will hide it lest she sees it和He hid it lest she saw it。但也很不普通。
2.在谈话里不用lest而用in case。
