The correct answer is C.
OBJ-2.2: When a cookie has the Secure attribute, the user agent includes the cookie in an HTTP request only if transmitted over a secure channel (typically HTTPS). Although seemingly useful for protecting cookies from active network attackers, the Secure attribute protects only the cookie’s confidentiality. Forcing the web application to use TLS or SSL does not force the cookie to be sent over TLS/SSL, so you still need to set the cookie’s Secure attribute. Hashing the cookie provides the cookie’s integrity, not confidentiality; therefore, it will not solve the issue presented by this question.