What Conclusion Can You Safely Draw When Someone Finishes an Exam

What conclusion can you safely draw when someone finishes an exam and turns it in when you are just halfway through?

A) The first test taker is probably the fastest reader in the class.
B) The first reader is satisfied that further time spent won't improve the score.
C) You are probably spending too much time on each test item.
D) The first test taker is probably more competent at test taking than you are.