Question 1130Navigation General

The correct answer is A) instrument used to measure relative humidity. A sling psychrometer is a device used to determine the relative humidity of the air. It consists of two thermometers - a wet-bulb thermometer and a dry-bulb thermometer. By comparing the temperatures measured by these two thermometers, the relative humidity can be calculated. This makes the sling psychrometer an appropriate instrument for measuring the moisture content in the air, which is a key factor in understanding maritime weather conditions. The other answer choices are incorrect because: B) a hydrometer is used to measure specific gravity, C) celestial navigation involves the use of sextants and chronometers, not a sling psychrometer, and D) a sling psychrometer is not a type of cargo gear.