What are the three categories that can be used to classify sources of information that may provide the enemy with advance warning?

The classification of sources of information that may provide the enemy with advance warning is primarily concerned with the aspects a military operation encompasses. The categories of operations, procedures, and communications directly relate to how military actions are carried out, the methods employed, and the means of sharing important information.

Operations encompass the overall strategy and maneuvers of a military unit, which could easily reveal plans to an observant enemy. Procedures refer to the standard methods used in an operation, which may leave traces or signals that can be intercepted or observed. Communications involve the transfer of information through various means, which, if compromised, could give an enemy significant insights into the intentions or movements of friendly forces.

The other choices, while related to military operations, do not specifically address the nature of information sources linked to advance warning. For example, assets, methodologies, and resources involve a broader range of concepts not exclusively related to warning indicators. Plans, contingencies, and logistics focus more on the preparatory and support aspects, rather than on direct operational insights. Similarly, strategies, forces, and intelligence may also emphasize broader concepts without pinpointing specific information sources that could lead to warnings about movements or actions.