Wednesday, May 26, 2010


Hi, Guys!,

Please, don't forget to study this before doing your homework. Remember: when you express
1.Obligation in the past, you use HAD TO.
2.Necessity or lack of Necessity in the past: You needed, you didn't need to, you didn't have to.
3. Ability in the past: COULD or WERE/WAS ABLE TO.

(Modal verb + have* + past participle)
*Have does not change

We use may have / might have / could have + past participle to talk about possibility in the past.
1. “Where was Sally last night?”
2. “I think she may have been at the cinema.” (= I think perhaps she was at the cinema)
3. “Peter is late.” “He might have missed the train.” (= Perhaps he missed/has missed the train)
4. “I can’t find my wallet anywhere.” “You could have left it at home.”
(= Perhaps you left/have left it at home)
5. “She walked straight past me without saying hello.”
6. “She might not have seen you.” (= Perhaps she didn’t see you)

We use should have / ought to have + past participle to say someone did the wrong thing in the past.
1. I should have done my homework at the weekend.
2. I’m really tired this morning. I shouldn’t have stayed up so late last night.
3. We had a really good time in London yesterday.
4. You ought to have come with us.

We use must have/ can’t have + past participle for deductions about the past.
Those shoes you bought are very nice. They must have been expensive. (= I’m sure that they were expensive).

1. You can’t have been at the swimming pool yesterday! It was closed all day!
(= It was impossible that you were at the swimming pool yesterday!

We can use couldn’t have …instead of can’t have ….here.
2. You couldn’t have been at the swimming pool yesterday!

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