What is required for the container in which classified materials are stored?

The requirement for a container used to store classified materials is that it must have a combination lock. This is essential for maintaining the security and confidentiality of the classified information. The combination lock ensures that only authorized personnel have access, thereby reducing the risk of unauthorized disclosure. By controlling access through a secure locking mechanism, the integrity of sensitive data is preserved, which is critical for national security and the protection of classified information.

The other options do not provide adequate security measures. For instance, using cardboard does not offer any physical protection or security against unauthorized access. Keeping the container open at all times would expose classified materials to potential threats and unauthorized individuals, compromising their integrity. Lastly, storing classified materials in public areas significantly increases the risk of exposure, making it impossible to safeguard the information effectively. Therefore, the requirement for a combination lock reflects best practices in security protocols for handling classified materials.