Which description best illustrates a 'hostile' contact in naval tactics?

A 'hostile' contact in naval tactics refers to any entity that is deemed a potential threat or adversary to friendly forces. An unrecognized military ship is categorized this way because it may be perceived as a possible adversary if its intentions or affiliations are unknown. In naval operations, understanding the nature of different contacts is crucial for threat assessment and tactical decision-making.

Identifying a military ship that is unrecognized implies a lack of information about its mission, capabilities, and allegiance, which could classify it as hostile until further intelligence can confirm its status. Other options are less likely to be classified as hostile in this context: a friendly vessel approaching is known to be an ally, an identified civilian aircraft typically poses no threat, and an ongoing training exercise does not involve hostile actions but rather is a controlled scenario among friendly forces.