Bob Smith is a little boy. On the first day at school, his teacher, Ms. Green, teaches him three words — you, he and I. Then the teacher says, “ I am your teacher. You are my student. He is your classmate. ” When school is over, Bob goes home. His mother asks him, “ What does your teacher teach you today? ” Bob says with a smile, “ Listen, Mom. I am your teacher, you are my student and he is your classmate. ” His mother says, “ No, dear. You are wrong. ” Then she says, “ I am your mother. You are my son. He is your father. ” The next morning at school, Bob ’ s teacher asks Bob to make sentences with the words “ you, he and I ” . Bob stands up and says, “ I am your mother. You are my son. He is your father. ”