What does NEC A15A train YNs specifically for?

The correct choice pertains to NEC A15A, which is designated for training Yeoman specifically to work on the personal staff of flag officers. This role involves a range of administrative and support functions tailored to meet the unique requirements of high-ranking personnel within the Navy. The training includes mastering the skills necessary to assist flag officers in managing their daily activities, correspondence, and official engagements, thus ensuring they operate efficiently and effectively.

The other options focus on different skill sets that are not the primary focus of NEC A15A. Filing and storage management is a part of general administrative duties, not specifically tailored to the unique needs of flag officers. Intelligence analysis involves a distinct set of skills related to information gathering and analysis, which falls outside the purview of a Yeoman's responsibilities. Lastly, security clearance processing is more associated with personnel ensuring appropriate clearance levels for access to sensitive information rather than the specific administrative support duties provided directly to flag officers.