Class, let's play a guessing game.Li Ming, you go first.
Li Ming:It's long and thin.What is it?Can you guess?
Wang Mei:Is it a ruler?
Li Ming:No, it isn't.You can write with it.
Wang Mei:A pencil?
Li Ming:Yes, you are right! Now it's your turn.
Wang Mei:It's big and black.It's on the wall.What is it?
Li Ming:It's a blackboard!
Wang Mei:Very good!