What distinguishes a wet store on an aircraft?

A wet store on an aircraft refers specifically to a storage area that is plumbed for fuel tanks. This means that it is designed to carry fuel, typically as part of the aircraft's capability to extend its operational range or provide additional fuel for other aircraft during in-air refueling operations. Wet stores are integral to military and aerial refueling operations, allowing aircraft to carry extra fuel or refuel others mid-flight.

The other options describe functions or capabilities that do not relate to the specific configuration of a wet store. For example, the containment of ammunition or surveillance equipment pertains to different provisioning and functionality requirements within the aircraft systems, separate from the capacity to store fuel. The role of carrying medical supplies also diverges from the definition of a wet store, which is strictly concerned with fuel storage and supply in relation to aircraft operations.