The correct answer is A) Vibration analysis. Condition-based maintenance relies on monitoring the actual condition of equipment to determine when maintenance should be performed, rather than relying on fixed time intervals. Vibration analysis is a key technique used in condition-based maintenance to detect potential issues with machinery before they result in equipment failure. By analyzing changes in vibration patterns, maintenance can be scheduled proactively based on the actual condition of the equipment. In contrast, options B, C, and D represent other maintenance approaches that are not based on condition monitoring, such as reactive maintenance after breakdown, time-based maintenance based on equipment running hours, or calendar-based maintenance intervals.