What type of mail must be sent to educational organizations or museums to qualify for a specific mailing price?

Library Mail is the correct answer because it is a special classification of mail that is designed specifically to meet the needs of educational institutions, libraries, and museums. This classification allows these organizations to send materials like books, printed music, and other educational resources at a reduced postage rate, making it more affordable for them to distribute information and resources.

Library Mail has specific eligibility criteria, ensuring that only items intended for educational purposes qualify for this special rate. This includes restrictions on the types of materials that can be sent and who the sender and recipient must be. The designation of Library Mail is aligned with the broader goal of supporting education and the dissemination of knowledge, which is crucial for libraries and museums in their role as educational entities.