What type of information is automatically declassified after a set period?

The correct choice identifies classified information that has a specific declassification schedule established by the authority responsible for its classification. This means that certain types of classified information are not intended to remain classified indefinitely and have a predetermined time frame after which they are automatically declassified, typically detailed in regulation or policy.

This process of automatic declassification ensures that information that no longer requires protection is made available to the public or relevant entities after the sensitivity of its content has diminished. This system serves to balance national security interests with the public's right to access government information, thereby promoting transparency once the information is no longer deemed sensitive or critical.

In the context of this question, other options do not correctly describe information that is automatically declassified after a designated period. Public information is already accessible and thus does not fall under the classifications that require a schedule for declassification. The notion that only top-secret information is automatically declassified is misleading because declassification can apply to any level of classified information as specified. Similarly, information labeled as restricted does not necessarily follow an automatic declassification schedule and might still be subject to ongoing restrictions based on specific circumstances or guidelines.