will or going to
Tom: 'We don't have any bread.' - Bob: 'I know. I.......some. I took some money from your purse.'
am going to
Tom: 'I'm really cold. '- Bob: 'I...... the heating on. ' (turn)
will turn
Tom: 'There's someone at the door. '- Bob: 'Oh, I........ it.' (answer)
will answer