Every friday, Bob is given a class test. The teacher doesn't check the students' answers by himself because there are 96 students in the class and he has other classes to manage as well. Instead, the teacher distributes those answer copies to other students in the same class such that no student gets his own copy. The teacher has a list according to which he distributes the copies. For example, Phineas always gets the copy of Ferb. And Ferb always gets the copy of Isabella. None of the students know who gets whose copy. That is, neither Phineas knows that he is checking the copy of Ferb, nor does Ferb know that his copy is being checked by Phineas. However, it seems like someone is having fun with Bob because Bob gets deducted marks even if his answers are correct.
How can Bob find out about the classmate who checks his copy every time, without letting the teacher know about it?
Some things to remember:
I took 96 arbitrarily.
I am not asking who. I am asking how can he find out about the classmate?
Isabella, Phineas and Ferb are just for examples. You can ignore them.
Just in case you think that I am Bob then I would say nope. This question just came to my mind accidentally.