What four switched networks are part of the defense communications system?

The correct choice identifies specific switched networks that are integral to the defense communications system. The Automatic Voice Network (AUTOVON) is crucial for providing a reliable and efficient voice communication system that can support military operations. It ensures that personnel can communicate across various locations, which is vital for operational effectiveness.

The Automatic Secure Voice Communications (AUTOSEVOCOM) network enhances this capability by providing secure voice communication channels that are essential for transmitting sensitive information without the risk of interception. The inclusion of "others" in this answer acknowledges that the defense communications system encompasses additional networks not explicitly named in the choice, which broadens the understanding of the diverse communication options available for defense purposes.

This answer reflects an accurate understanding of the landscape of military communications, focusing on both the established systems and the inclusion of other relevant networks, which may be classified or less commonly known.