Dont be late for the meeting next time， will you? (下次开会别迟到了，好吗?)
比较：I would remind you that smoking is forbidden here.
(表示"婉转的建议或请求"：我想提醒你，这里不能抽烟。)
neednt 的肯定式为must，例如：
You neednt see him， but I must. (你不必去看他，但我得去。)
cannot but 原形动词 (意思相当于have to)， 例如：
I cannot but tell you the truth. (我不得不给你说实话。)
2.情态动词的完成式：
情态动词的一般式用于表达"现在"或"将来"的情况，而情态动词的完成式则用来表达"已经发生的事情"，例如："你不应该来得那么晚。"这是对已经发生的事情(你来晚了)表示自己的看法：You
shouldnt have come so late.
将常用、常考的几个情态动词完成式列表说明如下：
must (not) have done表示对已发生的事情的"判断"，中文常表达为："准是…"It must have rained last
night; the ground is wet.(昨晚准是下雨了，地上湿漉漉的。)
should (not) have done / ought (not) to have
done表示"事与愿违"，中文常表达为："(不)该…"，"本(不)该…"The baby was cut badly; she shouldnt
(oughtnt to) have let him play with the scissors. (孩子伤得很厉害；她不该让他玩剪刀。)
may / can (not) have done表示"本(不)可能"She may have known the news; she is
crying. (她可能已经知道那个消息了；她在哭。)
need (not) have done表示"本(不)需要"You neednt have bought that dictionary; I
have got a spare one. (你实际上没有必要买那本字典；我有一本多余的。)
由于在没有情景的情况下很难区分情态动词一般式和完成式，例如"你不该去"，究竟是You shouldnt go there. 还是You shouldnt have gone there， 因此考试的时候往往会给出情景，这对判题非常重要，如上面表格例子中的"the ground is wet"，"the baby was cut badly"，"she is crying"， 都是题目所给的情景。