The theorem states: "The average of any two positive real numbers is also positive." Which facts are assumed and which facts are proven in a direct proof of the theorem?
a) Assumed: Positivity of real numbers; Proven: Positivity of the average
b) Assumed: Existence of real numbers; Proven: Positivity of the average
c) Assumed: The addition of real numbers; Proven: Positivity of the average
d) Assumed: Order property of real numbers; Proven: Positivity of the average