have to
have to加動詞原形
表示"不得不"、"必須"的概念。它比must更含有"客觀條件使得必須如此做"的意思，并有較多的時態(tài)。如：
Mr. Johnson has to work very hard to earn a living.約翰遜先生為了謀生不得不拼命干活。
I had to leave the party early last night. I wasn't very well.昨晚我只得早點離開晚會，我不大舒服。
We will have to get up very early tomorrow.我們明天必須起得很早。
I shall have to go to the clinic today for my bad cough.我咳嗽得厲害，今天必須去診療所看看。
[注]口語中的I have got to，you have got to等：I have to，you have to. Have I got to?和Do I have to?這兩種疑問形式均可用。
[英語語法手冊]情態(tài)動詞--shall
shall
shall作為情態(tài)動詞用于第二、三人稱
可表示說話人給對方的"命令"、"警告"、"允諾"、"威脅"等概念。如：
You shall do it，whether you want to or not. 不管你愿意不愿意，你必須做這項工作。(命令)
You shall have the book as soon as I finish it.這本書我一看完就給你。(允諾)
You shall pay for it.你一定會受到懲罰的。(威脅)
在疑問句中，情態(tài)動詞shall用于第一、三人稱
表示說話人征求對方的意見或向?qū)Ψ秸埵?。如?span lang="EN-US">
What shall I do now? 我現(xiàn)在該做什么?
Shall we go for a walk? 我們?nèi)ド⒉胶脝?span lang="EN-US">?
Shall he come tomorrow? 你要他明天來嗎?