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%

Entering standard psychrometric charts with a dry-bulb temperature of 78°F and a wet-bulb temperature of 68°F yields a relative humidity of 60%, indicating moderate moisture content in the lower marine boundary layer.