Дипломная работа: Modal verbs

We can use either the Present Perfect of the Present Perfect Continuous in this sentence.

In this meaning can is found in all kinds of sentences. It is followed by the simple infinitive and it refers the action to the present of future.

E.g. You can obtain a dog from the Dog’s Home.

Can we use the indefinite article with this noun?

We can’t use the indefinite article with this noun.

In past-time contexts the form could is used. It is followed by the simple infinitive in this case.

E.g. You could see the forest through the other window before the new block of houses was erected.

The form could in combination with the simple infinitive may also express unreality with reference to the present of future.

E.g. You could see the houses from here if it were not so dark.

In combination with the perfect infinitive, could indicate that the action was not carried out in the past.

E.g. You could have seen the house from there if it had not been so dark.

3) Permission

E.g. You can take my umbrella.

Can in this meaning is found in affirmative sentences, interrogative sentences in which a request is expressed, and in negative sentences where it expresses prohibition.

E.g. You can use my car. Can I use your car? You can’t use my car today.

In this meaning can is combined with the simple infinitive.

The form could with reference to the present is found only in interrogative sentences in which it expresses a more polite request.

E.g. Could I use your car?

The form could is found in reported speech (i.e. in accordance with the rules of the sequence of tenses).

E.g. He said that I could use his car.

He asked me if he could use my car.

4) uncertainty, doubt

E.g. Can it be true?

In this meaning can is found only in interrogative sentences (in general questions). Besides, sentences of this kind are often emotionally colored and so their application is rather restricted.

Depending on the time reference, can in this meaning is used in combination with different forms of the infinitive.

Thus, if reference is made to the present, the simple infinitive is found with static verbs.

E.g. Can he really be ill?