Deng Ling and Wu Ping wanted to visit their foreign teacher Melinda Watson on a Saturday. So around 8 o'clock one evening they went to her apartment. They could see that the lights were on and they could hear the TV. They were fairly sure that their teacher was at home.They knocked but no one came to open the door. They waited a moment and knocked again, but there was no response."I think she can't us with the TV on." Deng Ling said, and knocked harder. The were very puzzled and went away disappointed.