Mr. Li was in bed and was trying to go to sleep when he heard the bell ring . He turned on the light and looked at his clock. It was half past twelve. "Who can it be at this time of night?" he wondered. He decided to go and find out .So he got out of bed, put on his dressing gown and went to the door. When he opened the door, there was nobody there. "That's very strange." He thought. Then he went back to his bedroom, took off his dressing gown, got back into bed, turned off the light and tried to go to sleep. A few minutes later he heard the bell ring again. Mr. Li jumped out of bed very quickly and rushed to the door. He opened it, but again he found no one there. He shut the door and found a piece of paper with some words on it: "It is now after midnight, so it is April 1st. April fool to you!" "Oh, it was the English boy next door!" Mr. Li exclaimed, and almost smiled, He went back to bed and fell asleep immediately. The bell did not ring again. When he opened the door for the first time, there was   _   there.
a boy a piece of paper someone nobody