Which term best describes the boundary between air masses where cold air is replacing warm air, when considering the cold front?

• A. A low-power beacon at an ILS marker.
• B. A compass rose.
• C. Cold front.
• D. Compass locator.

Answer: (C)

A cold front is the boundary where cooler, denser air advances to replace warmer air. As this boundary moves in, the cold air undercuts the warm air, lifting it and often producing clouds and precipitation; you’ll typically see a drop in temperature and gusty winds as the front passes. This helps explain why pilots watch fronts closely, since the weather can change quickly around them and then improve after the front moves through. The other terms relate to navigation aids or chart features rather than weather boundaries, so they don't describe how air masses interact.