Keeping is to swallow

A busy mother asked her young son to take his baby sister out into the garden and look after her for half an hour while she was doing some work in the house.

The boy took the baby out, and they seemed to be playing quite happily when suddenly the mother heard the baby begin to cry, so she shouted to her son, 'Billy, what's the matter with Susan? Why's she crying?'

'Because she want wants my marbles,' answered Billy.

'Well, let her play with a few of them if it will stop her crying,' said the mother patiently. 'I must finish this work, and she'd be in my way in here.'

But she wants to keep to them!' answered Billy.

'No, she doesn't!' the mother said. 'She's only a baby. She's too young to understand anything like that.'

'But I know that she wants to keep them.' answered Billy. 'She's already swallowed two of them!'