A young mother and her little son get into a bus in the city The bus conductor(售票员) come to them for their money. The mother says, "I want one ticket to Oxford(牛津) And she gives the conductor money. The conductor looks at the small boy for a few seconds and then she says to the little boy. "How old are you, little boy? "The mother begins speaking, but the conductor stops her, and the boy says. "I am four years old at home but two and a half in buses and trains. "The mother's face turns red. She has to take out money and give it to the conductor.