A mother and her young son got on a bus and s     down. A girl, selling tickets on the bus, came to them. She was the conductor(售票员). The mother said，“I want a full ticket.” And t     she gave the conductor some m     . The conductor looked at the little boy and a     , “How old are you?” The mother wanted to speak, b      the conductor stopped h    , and the boy said, “I’m six years old at home, and four years old on b      and trains. My mother told me that.” The mother’s face turned r    . She had to take some more money o      of her bag and gave it to the conductor. The conductor gave her a full ticket and a half-price o     .

s	t	m	a	b
h	b	r	o	o