Which of the following components of COMSEC focuses on the security of transmitted signals?

Transmission security is the correct response because it specifically addresses the protection of transmitted signals during communication. This aspect of COMSEC involves measures and techniques designed to prevent unauthorized interception or exploitation of signals as they are being transmitted. By focusing on the security of the signals themselves, transmission security ensures that even if an adversary is in proximity to the communication channel, they would not be able to decode or understand the content being exchanged.

Other components of COMSEC serve different roles: physical security pertains to the safeguarding of physical assets and infrastructure from unauthorized access or attack; operational security focuses on protecting sensitive information concerning operations and activities to prevent it from falling into enemy hands; and emission security deals with the prevention of unintentional signals that may be emanated during communications. Although all these components are essential for comprehensive communication security, transmission security is uniquely centered on the safety of the signals themselves during transmission.