Adevice that uses the wet/dry bulb method to measure the the sling psychrometer. as seen here, two thermometers are attached to a handle or length of rope and then are spun around in the air for a few minutes.

a) air currents

b) air temperature

c) light intensity

d) relative humidity

I would say the answer is D

A hygrometer is an instrument used to measure relative humidity. ... To determine the relative humidity, the temperatures are taken from the dry-bulb thermometer and the temperature difference between the wet and dry bulb thermometers.

hygrometer is a weather instrument used to measure the amount of humidity in the atmosphere. There are two main types of hygrometers -- a dry and wet bulb psychrometer and a mechanical hygrometer.

b.

explanation: