Astonishment and improbability

1. Can/could also convey the meaning of uncertainty, doubt, and astonishment (these meanings are closely connected).

Could is used to imply more uncertainty: Could it be time?

They are used in combination with different forms of the Infinitive and are found only in interrogative sentences (general questions): Can he really be ill? Can it be true? Can she be singing in the next room? Sentences of this kind are often emotionally coloured, and in Russian this construction is rendered as: Неужели? Неужели это правда? Неужели он болен? и т.д.

NOTE:

· Can/could + Perfect Infinitive (or Perfect Continuous Infinitive) are used to refer the action to the past: Can he have told a lie? Could she have been waiting for us so long?

2. Can/could are also used to talk about improbability and are found only in negative sentences (all forms of the Infinitive are possible): It can’t be true. She can’ t be singing in the next room.

NOTE: Can’t + Perfect Infinitive is used to refer the action to the past: He can’t have told a lie! Couldn’t is also used in this meaning to make the statement less categorical: She couldn’t have told a lie! In Russian it is rendered as: Не может быть, чтобы… Вряд ли это так…

§ 4 Can/could to express permission, requests,