You've been a great help, I must say.

　　依我看，你真是幫了個大忙啊。

　　I must go to the bank and get some money.

　　我得上銀行取點兒錢。

　　He must be 70 if he's a day!

　　他至少70歲了！

　　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。