[译] 你们上课一定不要迟到。
[误] It is imperative that you are not late for class.

[正] It is imperative that you should not be late for class.
[注] 在It is imperative that...（有必要……）的句型中，that从句中的谓语动词必须用虚拟语气，即“should+动词原形”。