A work ill done must be twice done.

I must do this and I must do that.

我必须做这必须做那。

What must be done, must be done.

必须做的事情就必须做。

We must do all that is to be done.

我们必须做该做的事。

promise to do what is needful

答应做必须做的事.

I'll do what I must.

我必须做我该做的事。

be necessary (for one) to do something (go somewhere)

（某人）必须做某事（去某处）

We are now under the necessity of doing the work.

我们现在必须做这工作。

You must do it beyond all things.

你首先必须做这件事。

He must do his homework everyday.

他每天必须做功课。

We must be prepared for the worst.

我们必须做最坏的打算。

The user knows what must be done;

用户清楚必须做什么。

I must do something to stop them.

我必须做什么来阻止。

You MUST do your maths homework.

你必须做数学作业。

He is to do his share of work .

他必须做他份内的工作。

We must have a plan, must not we ?

我必须做个计划，对吗?

This is the exercise we must do .

这是我们必须做的练习。

Is there anything that I have to do?

有什么必须做的事吗？

We must reconcile our statements with our conduct.

我们必须做到言行一致。