The correct answer is C) 5 years and must be renewed. The credentials issued by the U.S. Coast Guard for apprentice mate (steersman) of Towing Vessels are valid for 5 years before they need to be renewed. This is in accordance with the regulations outlined in 46 CFR 11.463, which specify the validity period and renewal requirements for this credential. The other options are incorrect because 2 years (A) and 3 years (B) are not the valid duration for this credential, and "None of the above" (D) is not the correct answer since option C is the right one.