【初中·阅读理解·The Broken Window】
Tom and his friends were playing football in the street when the ball hit Mr Black's window. The glass broke. All the boys ran away except Tom.
He knocked on the door and told Mr Black what had happened. Mr Black looked at the broken window and then at Tom's face. "Are the others coming back?" he asked. Tom shook his head.
"Then you can pay for it," said Mr Black. "That is five dollars. You may work for me after school — two dollars an hour."
Tom worked for three afternoons. On the last day Mr Black gave him the five dollars back. "Keep it," he said. "This is for telling the truth. Honesty is worth more than a window."

第 3 题：What did Mr Black want to teach Tom?（　　）