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 also has no positive factor in common with n other than 1. If p is a prime number then f(p) =
A) p-1 B) p-2 C) (p+1)/2 D) (p-1)/2 E) 2 这题我压根没读懂...那句纠结的in common with n other than 1。。。 多谢大家