Have to do something often

必须───must;经常───often

The stew must be boiled up before serving.───炖肉必须煮熟才能上桌.

The wicked must be wiped out.───恶人必须除掉.

I can't explain such a statement by him on the basis of logic. He must have blown his top.───我从逻辑推理方面解释不了他讲的这番话,他想必是神经错乱了.

Only a few students passed the exam, so you can see that the paper must have been extremely stiff.───只有几个学生通过了考试, 可见考题是很难的.

There must be something wrong with my left arm, which is asleep.───我的左臂发麻,一定出什么问题了.

Hospital operating instruments must be sanitary.───医院的手术器械必须是消过毒的.

This structure must be stable.───这种结构一定很稳固。

We are in the same boat; we must help each other.───我们既然同舟, 就要共济.

There must be an error in our calculations.

We must make massive efforts to improve it.

We must reinforce the troops at the front.

We must stock up for the winter.

A full cup must be carried steadily.