OPSEC is concerned with:

a. Identifying and controlling classified information.
b. The daily administrative activities associated with military operations.
c. Identifying, controlling, and protecting unclassified information that is associated with specific military operations and activities.
d. Controlling the operations of daily activities.
e. Identifying and controlling classified and unclassified information.

C. Identifying, controlling, and protecting unclassified information that is associated with specific military operations and activities.

Explanation:

OPSEC which is an acronym for Operations Security is tasked with identifying critical information and analysing if they are important to enemy intelligence, protection of such information and preparation of countermeasures if necessary.

Operations Security has to do with general unclassified information about military operations and activities which might give the enemy an advantage.

Countermeasures to letting critical unclassified information reach enemy nations involved the use of mail encryptions, analysis of pictures taken to ascertain of there are details in the background that could give strategic information, and generally keeping a closed mouth over social media.

answer; communication channel;