The function f is defined for all positive integers n by the following rule:
f(n) is the number of positive integers each of which is less than n and has no positive factor in common with n other than 1. If p is any prime number the f(p)=
I'd say it's A, p-1. If p is prime then every positive number less than p fits the criteria of the function, even 1. (1 has no factor in common with p other than one) To visualize this one I chose p=17.