The correct answer is A.
OBJ-2.4: HMAC-based One-time Password Algorithm (HOTP) is an algorithm for token-based authentication. The authentication server and client token are configured with the same shared secret. The token could be a fob-type device or implemented as a smartphone app. The token does not have an expiration under HOTP, but an improved version known as TOTP does include token expirations.