【单选题】

Six people were traveling in a compartment(车厢)on a train. Five of them were quiet and well behaved(举止端庄), but the sixth was a rude young man who was making a lot of trouble to the other passengers.

At last this young man reached his station and got off with his two heavy bags. None of the other passengers helped him, but one of them waited until the rude young man was very far away, and then opened the window and shouted to him, "You left something behind in the compartment. "Then he closed the window again.
The young man turned around and hurried back with his two bags. He was very tired when he arrived, but he shouted through the window. "What did I leave behind "
As the train began to move again, the passenger who had called him back opened the window and said, "A、very bad impression(印象)!\
The story tells us that ______ .A．young people should be well behaved on a train
B．people with bad behaviour are not welcome
C．it is easy to leave something on a train