When the teacher entered the class little Jonny slowly said:
“Sir excuse me; your zipper is open.”
So the teacher thanked him and fastened his zipper.
He went near little Jonny and told him:
“My dear it would better to say: the office door is open.”
The next day when the teacher entered the class, unfortunately, his zipper was again open!
Little Jonny loudly shouted:
“Not only the office door is open but also the teacher is at the door and two small students are beside him.”