Computer Networks: The total number of keys required for a set of n individuals to be able to communicate with each other using secret key and public key crypto-systems, respectively are: (A) n(n-1) and 2n (B) 2n and ((n(n – 1))/2) (C) ((n(n – 1))/2) and 2n (D) ((n(n – 1))/2) and n