The dry-bulb temperature is 78°F (26°C) and the wet-bulb temperature is 68°F (20°C). What is the relative humidity?

Correct Answer: Option D — 60%

According to Bowditch, relative humidity is determined using psychrometric tables by comparing dry-bulb and wet-bulb temperatures. With a 78°F dry-bulb and 68°F wet-bulb, the depression is 10°F, corresponding to 60% relative humidity in standard meteorological tables.