This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
Which of the following regions has the lowestatmospheric humidity? 
Select and explain. 
A. Equatorial, B. Monsoon, C. Prairies, D. Polar
D: Polar
Answer: D: Polar 
Explanation: Humidity or moisture is always present in the atmosphere. The amount of moisture which air can hold depends upon its temperature. If air is cooled excessive moisture precipitates for a paicular temperature. This is called the dew point.