It was half past twelve at night.Mr.Black ____ not fall asleep.He was lying in bed and listening to the music ____ he heard the bell.He turned ____ the music and got up."Who can it be at this time of night?" he said to himself.When he ____ the door,there was nobody there."That's really very strange," he ____.Then he returned to his bed.While he was falling asleep a few minutes later,he heard the bell ____.Mr.Black jumped out of ____ and ran to the door.He opened it,but again he didn't find ____ there.He shouted,"Don't do that.If you do again,I'll get annoyed." He closed the door and then he found a piece of ____ on the floor.There were some words on it,"I'm the boy next door.It is a new day now,____ it?It is April 1st." Mr.Black laughed.