The correct answer is A: When incidental to an authorized retransmission of manned spacecraft communications. According to FCC Part 97.113(c), music may be transmitted using phone emissions only when it's incidental to retransmitting communications from manned spacecraft (like the International Space Station). This is a very narrow exception. When astronauts on the ISS or other manned spacecraft communicate, and that communication happens to include music (perhaps as background, or as part of a scheduled event), amateurs may retransmit those communications, including the incidental music. However, you cannot simply play music on amateur frequencies for entertainment or any other purpose. This exception exists to allow amateurs to relay interesting space communications to others who might not be able to receive them directly.