_________ is a cipher formed out of substitution where for a given key-value the cipher alphabet for every plain text remains fixed all through the encryption procedure.

A) Playfair Cipher

B) Caesar Cipher

C) Polyalphabetic Cipher

D) Monoalphabetic Cipher

Correct Answer : Monoalphabetic Cipher

Explanation : Monoalphabetic cipher is a cipher formed out of substitution where for a given key-value the cipher alphabet for every plain text remains fixed all through the encryption procedure.