情态动词：could、would 和 should

Could you open the window, please? Use could to ask for permission politely. Example: could you lend me 10 pounds, please?

You can use should to give advice, but not to ask for permission politely. Example: you should buy new shoes.

Use must to give an order, but not to ask for permission politely. Example: you must clean your room before you leave.

I would like to order a steak, please. Use would like to express your desires or preferences. Examples: I would like an apple; I would like to go on holiday.

You can use could to make a polite offer, but not before like to express a desire. Example: we could help you. 

Use should to give recommendations and make suggestions, but not to express your preferences. Example: she should speak to her parents.

We should get ready. Use should to make a suggestion politely. Example: you should try to convince him.

You can say You have to get ready to express an obligation, but you cannot do it here because to is not present in the sentence.

To put means to place something in a specific position… but you cannot use it in this sentence. Example: I will put the milk in the fridge.

I would like an ice-cream, please with would like to express that you desire something, in this case an ice-cream. Note: use please at the end to make your request more polite. Example: I would like to improve my English.

Could you pass me the bread, please? with could to make a polite request. Example: could you tell me the password, please?

You have to eat vegetables. Use have to To have, present simple tense + infinitive without to (here, to eat) to express an obligation. Example: you have to exercise more.

(To) have means to possess and we do not use it right before an infinitive without to (here, eat). Example: I have a nice room.

You could say you need to eat vegetables to express a necessity, but in this sentence to is missing.

He needs to stop, with needs to to express a necessity. Example: I need to go on holiday!

We could say I need to stop, but since the subject is he, we have to use needs with an -s at the end.

A needle is used for sewing… and not in this sentence! Example: I need a needle to sew on a button.

Guests don't have to clean their rooms, with the negative form don't have to because guests are not required to clean their rooms. Example: you don't have to work until late.

You could say, for example, the guests haven't got their room key, but we generally don't use the negative form with got to talk about obligations.

You could say there is no need to clean your room (=it is not necessary to clean your room), but you cannot use this expression after guests.

Magda should always be kind to guests. In this case, should is used to give a piece of advice politely. Example: you should eat healthy food.

You could say Magda wants to be kind to guests to express her wish or goal, but you cannot use want in this sentence because, after a subject like Magda (=she), you would need to use wants. Also, want cannot be used before always be.

You could say Magda needs to be kind to guests (with needs with an ‑s at the end) to express a necessity, but you cannot use need in the structure of this sentence.

We would like some water, please. We use would + like to express a desire and to ask for what we desire politely (in this case, some water). Example: I would like a salad, please.

Should is used to give recommendations, but not to express our desires politely. Example: you should buy a thicker coat for the winter.

You can use could to ask for permission politely, but not to express your desire or preference. Example: could you help me, please?

Could you call Roger, please? with could, which in this case is used to make a polite request. Example: could you repeat that, please?

You can say you should call Roger if you want to give a recommendation, but in this sentence we want to make a polite request.

Use must to give orders, not to make polite requests. Example: Roger must work 8 hours a day!

Caroline has to cook To have, present simple tense, which means that Caroline has an obligation to cook. Note: remember that the verb to have is irregular.Example: Roger has to work 8 hours a day.

You could say I have to cook, but since the subject here is Caroline (=she), the verb to have becomes has To have, present simple tense.

🎵 Heaven, I'm in Heaven… 🎵 Maybe you like Fred Astaire too much… Unfortunately, this is not how we complete this sentence!

We need to go home. Use need to to express a necessity. Example: they need to finish earlier.

You could say we need some help, with need + noun (some help) to talk about what you require, but here you also need the word to before the verb go.

You could say we don't need to go home, but to is missing in this option.

Do you have to inform them? When forming a question, have to follows the same rules as any other verb, so follow the structure: do + subject (you) To do, question + modal verb (have to) + infinitive without to (inform). Example: do you have to send him a report?

You could say you have to inform them in the affirmative form, but this sentence is a question.

You could say you have to do your chores with have to + the verb do, but here we already have the verb inform, so we cannot add another infinitive without to.