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
Asmann psychrometer is useful for - 
Select and explain. 
A. Humidity, B. Velocity, C. Temperature, D. Sound intensity
A: Humidity
Answer: A: Humidity 
Explanation: A psychrometer is an instrument to measure the humidity of the air. Assmann psychrometer is a poable instrument to give accurate readings of wet and dry bulb temperatures of air. In this instrument, the air is drawn at a speed of 5 meters per second by clockwork fan. Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 809