This problem will check your understanding of the concept of functions. Let me remind you the definition of a function:

** Definition of a Function:**
A function is a rule or correspondence which
associates to each number x in a set A a
** unique **
number f(x) in a set B.

Which of the followings can not be
a function?

** A. ** T(t)is the temperature
of hot water after time t.** B. ** N(x) is a person whose last name is
John** C. ** P(t) is the human population of the world
at time t** D. ** C(w) is the set of mailing a first-class
letter with weight w.** E. ** All of the above** F. ** None of the above

Your overall score for this problem is