Which of the following cryptographic methods is a monoalphabetic cipher?

A.
Caesar Cipher

B.
Vernam Cipher

C.
Vigene`re Cipher

D.
Jefferson Disks

Explanation:
Answer A is correct; the Caesar Cipher is a monoalphabetic rotation cipher that shifts each character forward by 3.

Incorrect Answers and Explanations: B, C, and D: Answers B, C, and D are incorrect. The Vernam Cipher is a one-time pad. The Vigene`re Cipher is the first polyalphabetic cipher. Jefferson disks used many disks, each with its own alphabet, and is therefore polyalphabetic.