Question 893Navigation General

The correct answer is D) sling psychrometer. A sling psychrometer is an instrument used to measure the relative humidity of the air, which is a key factor in predicting the formation of fog. By measuring the difference between the wet-bulb and dry-bulb temperatures, the sling psychrometer can calculate the relative humidity and dew point, providing valuable data for forecasting the likelihood of fog development. The other options are not as directly useful for fog prediction. An aneroid barometer measures atmospheric pressure, an anemometer measures wind speed, and a microbarograph is a device that continuously records changes in atmospheric pressure - while these can provide helpful meteorological data, they are not as specific to the humidity conditions that lead to fog formation.