A teacher stood in front of his history class of twenty students just before handing out  the final exam. His students sat quietly and waited for him to speak. "It's been a pleasure teaching you this term," he said. "You've all worked very hard, so I have a pleasant surprise for you. Everyone who chooses not to take the final exam will get a "B" for the course." Most of the students jumped out of their seats. They thanked the teacher happily, and walked out of the classroom. Only a few students stayed. The teacher looked at them. "This is your last chance," he said. "Does anyone else want to leave?" All the students there stayed in their seats and took out their pencils. The teacher smiled. "Congratulations  ," he said. "I'm glad to see you believe in yourselves. You all get 'A's." Why did some students stay in their seats?
Because they were afraid to leave. Because they wanted to take the exam. Because they didn't have anything to do. Because the teacher told them to stay in their class.