Bob is six years old．He is old enough to go to school． On the first day，his teacher taught him three words，“I，you，he”．Then the teacher said，“I am your teacher．You are my student．He is your student. He is your classmate.”When school was over，Bob went home. His mother asked him，“What has your teacher taught you today?”Bob said with a smile，“Listen，Mum and Dad，I am your teacher．You are my student．He is your classmate．”His mother said，“No，dear．You’re wrong．”Then she said，“I am your mother．You’re my son．He’s your father．”The next day，Bob’s teacher asked Bob to make sentences with “I，you and he”．
Bob stood up and said，“I’m your mother．You’re my son．He is your father．”All the students in Bob’s class laughed．