Tom is seven .He goes to school every day.The school is near his home,so he gose there on foot and comes back home on time.But today he is late.His mother asks him,
"Why are you late today?"
"I am in the headmaster's office."
"Because my teacher asks us a question in the class.Nobody can answer it,but I can."
"It's good to answer the teacher's question."
"But the question is, Who puts ink on my chair?"