Postal Service Practice Exam

The correct choice identifies a restriction on media mail, which is designed for shipping media items such as books, audio recordings, and educational materials at a lower cost. One of the key limitations of media mail is that it cannot be used to send personal correspondence, like personal letters or postcards. This policy ensures that media mail remains a cost-effective option specifically for educational and informational media, rather than general communications.

While there are indeed specific packaging rules that media mail must conform to, such as size and weight restrictions, these do not match the primary nature of the restriction like the prohibition against personal letters.

Additionally, the types of items eligible for media mail include educational materials but not exclusively those; in fact, other types of media items are permissible. As for the weight limitation, while there is a maximum weight allowance, it's set at 70 pounds, far exceeding the 5-pound claim. Thus, the restriction on sending personal letters is a definitive and clear guideline within the regulations governing media mail.