must的過去式和過去分詞形式

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。