must的過(guò)去式和過(guò)去分詞怎么寫(xiě)

　　You must signal which way you are going to turn.

　　你要朝哪個(gè)方向轉(zhuǎn)，必須發(fā)出信號(hào)。

　　You're a great help, I must say!

　　我得說(shuō)，你可沒(méi)少幫忙！

　　There must be a way around the problem.

　　肯定有解決這個(gè)問(wèn)題的辦法。

　　The work must be completed within a certain time limit.

　　這項(xiàng)工作必須在一定期限內(nèi)完成。

　　There is a growing realization that changes must be made.

　　越來(lái)越多的人認(rèn)識(shí)到改革勢(shì)在必行。