When a Yes/No question is asked, we use the auxiliary on its own when answering rather than repeating the whole verb form.
'Will it rain this afternoon?' 'Yes, I think it will.' (rain this afternoon)When we make comments in conversation, we usually avoid repeating information that has just been given.
'Mary's coming.' 'I know she is.''Angela can speak Russian and Hungarian.' 'She can't, can she?'To know which auxiliary verb to use, it is necessary to reconstruct the part of the sentence that is missing, and to consider carefully the meaning and the time of the events in the sentence.
When there is more than one auxiliary, we can use one or more when responding. We always use more than one if there is a change in auxiliary.
'You should be given a rise.' 'Well, I haven't.''She can't have told him yet.' 'She must have.'We can use to instead of the full infinitive in replies.
'Haven't you done the washing-up yet?' 'No, I'm just going to.''Are you coming for a walk?' 'No, I don't want to.'The verb to be is not usually reduced to to.
She's less moody than she used to be.I wasn't as impressed as I'd expected to be.