A professor stood before his class of twenty senior organic biology
students, about to hand out the final exam.

"I want to say that it's been a pleasure teaching you this semester.
I know you've all worked extremely hard and many of you are off to
medical school after summer. So that no one gets their GPA messed up
because they might have been celebrating a bit too much this week,
anyone who would like to opt out of the final exam today will receive
a 'B' for the course."

There was much rejoicing in the class as students got up, walked to the