Final answer:
Wind direction is a condition specific to tactical ventilation that should be communicated to crew members and/or a supervisor because it significantly impacts how the fire spreads and the success of ventilation operations.
Step-by-step explanation:
The question pertains to a condition that is specific to tactical ventilation which should be communicated to crew members and/or a supervisor. Tactical ventilation is a process used by firefighters and emergency services to control the flow of air in a burning structure. The correct answer to the question is choice (a), Wind direction. Wind direction is crucial as it affects how the fire will spread and the effectiveness of the ventilation efforts. While relative humidity and temperature outside the structure are also important factors in fire behavior, wind direction can have a more immediate and significant impact on tactical ventilation strategies.