Question

which is associated with low humidity? dry air warm air rainforest coastal area

Explanation:

Humidity refers to the amount of water vapor in the air. Dry air has less water vapor, so it has low humidity. Warm air can hold more moisture (higher humidity when saturated, but just "warm air" itself isn't directly low - humidity by nature). Rainforests and coastal areas generally have high humidity due to abundant water sources (like frequent rain in rainforests and proximity to water in coastal areas which evaporates and adds moisture to the air).

Answer:

dry air