Tom is seven. He goes to school every day. The school is near his home, so he goes there on foot and comes back home on time (及时). But today he is late. His mother asks him, "Why are you late today?"
"I am in the headmaster's office."
"Why do you go to 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 questions. I'm proud (自豪的) of you."
"What's the question?"
"Who puts ink on my chair?"