Carol and Susan were great friends. They were in the same class at school, and they often visited each other's homes at week-ends.
When they were both eight years old, Carol's mother had a baby. Carol was overjoyed to have a little sister and was always talking about her to Susan, who had no brother or sisters.
At first Susan was very interested in the new baby, but after some time she began to get rather discontented with Carol's continual talking about it. She also felt a little jealous.
One morning when the two girls were in the school playground, Carol said to Susan cheerfully, 'Do you know, Sue, my baby sister gained nearly two hundred grams in weight this week.'
'That's not very much,' answered Susan. 'I know a baby that gains five kilograms a day.'
'Oh, that can't be true!' answered Carol scornfully. 'Whose baby is it?'
'An Elephant's said Susan.