You must signal which way you are going to turn.
你要朝哪個方向轉，必須發出信號。
You're a great help, I must say!
我得說，你可沒少幫忙！
There must be a way around the problem.
肯定有解決這個問題的辦法。
The work must be completed within a certain time limit.
這項工作必須在一定期限內完成。
There is a growing realization that changes must be made.
越來越多的人認識到改革勢在必行。