Which statement is true regarding the mailing of controlled substances?

The statement that controlled substances can be mailed using the United States Postal Service is accurate. Under federal regulations, controlled substances can be shipped through the postal system as long as certain conditions are met. This includes ensuring that the substances are properly packaged, labeled, and that both the sender and recipient comply with the legal requirements governing controlled substances.

The United States Postal Service allows for the mailing of controlled substances as part of the legitimate distribution of medications, which includes prescriptions sent by pharmacies to patients. However, it is important for senders to adhere to all federal and state laws regarding the mailing of these substances to ensure compliance and to avoid any potential legal issues.

Furthermore, while only registered entities can handle controlled substances, this includes pharmacies, manufacturers, and some other authorized entities. The key point here is that the mailing itself is permissible under specific guidelines, which is why the correct choice emphasizes the postal service's allowance for this activity.