Explanation: Every examination for the code portion of a radiotelegraph license must ensure the applicant can accurately send and receive all fundamental characters used in Morse code communication. This comprehensive approach is essential because operators need to handle various messages, not just specific types. Option D correctly lists these required elements: all alphabet letters, all numerals, common punctuation marks (period, comma, question mark, slant mark), and crucial prosigns (AR for "end of message," BT for "break/pause," and SK for "end of contact"). This complete set forms the foundational knowledge required for general radiotelegraphy. Options A, B, and C are incorrect because they focus on specific *applications* (shipboard messages, distress signals) rather than the entire *character set* that the examination must cover. While these applications are vital for an operator's duties, the code proficiency test itself must first establish a command of all the building blocks of Morse code transmission and reception.