Obligation and advice: should/ought to/shall/had better

SHOULD and OUGHT TO are used:

1) to talk about mild obligation and duty to do something.

We should send them a postcard.

He ought to come more often.

2) to ask for and give advice.

What do you think I should/ought to do?

She oughtn't to/shouldn't marry him.

NOTE:

1. Should and ought to are very similar in meaning but we often prefer ought to to talk about authority which comes from outside the speaker, e.g. from laws or rules.

You ought to pay your bills regularly.

2. Should is more common than ought to.

Exercise 14. Complete the sentences with should/ought to and the words given.

Example: These windows are dirty. (you/clean them/more often)

You should/ought to clean them more often.

1. Ted drives too fast. (he/drive/more carefully)

2. There won't be much food at the party. (we/take something/to eat?)

3. It's going to be a cold day. (you/wear/an overcoat)

4. Pam is a bit overweight. (she/not eat/between (meals)

5. She owes you a lot of money. (you/not lend her/any more)

6. Julie looks run down. (she/not go/to bed late every day)

SHALL is used:

to ask for advice or instructions

I'm not sure what to do. Shall I apply for the job or not?

How long shall I cook this meat?

Exercise 15. Complete each sentence. Use shall I and the most suitable verb.

paint

get

tell

say

put

Example: Who shall I invite to my party?

1. How much money from the bank?

2. Where all these dirty plates?

3. What do you think? my friends what has happened?

4. What colour my living room?

5. What if someone asks for you?

HAD BETTER ('D BETTER) is used:

to express mild obligation and advice.

It's going to be cold tonight.

We'd better turn on the heating.

You'd better not be late for work today.

Exercise 16. Complete the sentences using had better and the verbs in the box.

Not leave

Take

Park

Not eat harry

Be answer

Example: The phone is ringing. I'd better answer it.

1. You a pullover with you. It's getting colder.

2. Oh no! Look! There's "No Parking" sign here. We somewhere else.

3. I'm late. I .

4. This knife is very sharp. You careful when you use it.

5. There's a lot of crime in this area. We any doors or windows unlocked.

6. I've put on weight lately I between meals.

Possibility: can/could/may/might

CAN is used:

1) to say that something is possible (circumstances permit)

Anyone can learn to swim.

Can you get to the top of the mountain in one day?

2) to express occasional possibility (= sometimes)

The flu can be quite dangerous. (Sometimes it is quite dangerous.)

Exercise 17. Complete the sentences. Use can and the most suitable verb.

cause

ski

make

live

reach

survive

Example: In some cases this can cause difficulty.

1. You on the hills.

2. Anyone mistakes.

3. Temperatures near the South Pole minus 43 degrees centigrade.

4. Camels for up to 17 weeks in the desert without water.

5. Monkeys for up to 40 years.

Exercise 18. Make suitable sentences from the table below. Use can to express occasional possibility.

Example: George can sometimes be very unreasonable.

George				not objective.
Travelling				tricky.
My sister	can	sometimes	be	boring.
Some grammar rules		often		very unreasonable.
Mass media				very nice.

MAY/MIGHT/COULD are used to talk about present or future possibility.

MAY MIGHT COULD

+ BE/DO (Present Infinitive) or BE … -ING (Present Continuous Infinitive)

NOTE:

Might slightly increases the doubt.

Could increases the doubt more than may and might.

He may/might/could tell his wife. (Perhaps he tells/will tell his wife.)

They may/might/could be having dinner now. (Perhaps they are having dinner now.)

Exercise 19. Rewrite these sentences. Use may/might/ could to express present or future possibility.

Example: Perhaps my parents will be at home tomorrow. My parents may/might/could be at home tomorrow.

1. Perhaps you are right.

2. Perhaps she will be working today.

3. Perhaps Liz will help us if we give her a ring.

4. Perhaps they don't know the address.

5. Perhaps I'll see him on Monday.

6. Perhaps he's waiting at the station.

MAY/MIGHT/COULD are used to talk about past possibility.

MAY		HAVE BEEN/DONE (Perfect Infinitive)/ HAVE BEEN DOING (Perfect Continuous Infinitive)
MIGHT	+
COULD

He may/might/could have heard it from Jack. (Perhaps he heard it from Jack.)

They may/might/could have been working yesterday. (Perhaps they were working yesterday.)

NOTE:

We also use might/could (but not may)+ Perfect Infinitive to say that something was possible in the past but did not happen.

"I forgot to lock my front door last night." — "You were very lucky. Someone might/could have broken into."

Exercise 20. Rewrite these sentences. Use may/might/ could to express past possibility.

Example: They have left already.

They may/might/could have left already.

1. Mr. Smith went on business to France last night.

2. He has been working all day.

3. She didn't catch the 8 o'clock bus.

4. The secretary forgot about the meeting.

5. They left early.

Exercise 21. Complete the sentences with may/might/ could to express possibility in the past. Use the words in brackets.

Example: Where was Sally last night? — (she/be/at the cinema)

She may/might/could have been at the cinema.

1. She walked straight past me. (she/not see/me)

2. I can't find my purse anywhere. (I/leave/at home)

3. John is late. (he/miss/the train)

4. What was Peter doing yesterday? (he/work)

5. What has Sally had for breakfast? (she/have/bacon and eggs and a cup of tea) 6. What did that ear cost? (it/$5,000)