Nancy likes to take a walk in the park at the weekends. Now she is taking a walk with her good friend Yang Ling. There are many different signs in the park. Nancy knows a lot about them. Suddenly she sees a short man walking on the grass. She points to the sign and says to him "Sir, look at the sign! You can't walk on the grass." The man smiles and says "You're right, young girl. But I'm the park keeper. I look after the grass. I'm picking up the garbage on it."
