You will be given a definition of a task first, then some input of the task.
In this task, you are given an impractical statement. You are also given three reasons (associated with "A", "B", "C") explaining why this statement doesn't make sense. You must choose the most corresponding reason explaining why this statement doesn't make sense.

Nail is a small piece of metal which is inserted into a lock and turned to open or close it
(A) Usually nail is made up of iron
(B)Nail can be used to hang something on the wall
(C)Usually people use key to unlock a lock
Output:
C