- 我一定要马上去吗？
Must I go there at once?
- 这封信一定要用英文写吗？
Must this letter be written in English?
- 选择朋友一定要十分谨慎。
You should choose your friends very carefully.
- 我们一定要保持双手清洁。
We must keep our hands clean.
- 我为什么一定要那么做？
Why do I have to do that?
- 你想去美国读书的话，一定要先申请一张学生签证。
If you want to study in the United States, you need to get a Student visa.
- 一定要熄了火，然后再离开。
Be sure to put out the fire before you leave.
- 我一定要在明天前把书还给他。
I must give back the book to him by tomorrow.
- 你一定要好好记住。
You must bear it in mind.
- 地板一定要保持乾净。
The floor must be very clean.
