A function N (S) is said to have a pole (or zero) at infinity

A function N (S) is said to have a pole (or zero) at infinity if the function N (1/S) has a pole (or zero) at S = ?
A. ∞
B. 2
C. 0
D. 1
The correct option is C. 0

To elaborate: A function N (S) is said to have a pole (or zero) at infinity, if the function N (1/S) has a pole (or zero) at S = infinity. A zero or pole is said to be of multiplicity ‘r’ if (S-Z)^r or (S-P)^r is a factor of P(s) or Q(s).