Answer:
C. relative humidity
Explanation:
Sling psychrometer are instruments which have the purpose of determining the relative humidity level in the air. It has two types of thermometer that helps to carryout these functions, the wet-bulb and the dry-bulb.
The wet-bulb temperature is recorded by a thermometer whose bulb is enclosed in a wick holding moisture and is spun rapidly in air.
The dry-bulb has an air temperature recorded by a dry thermometer.
Thus, if a boater is still wondering if it will rain and she uses a sling psychrometer to measure the moisture content of the air relative to the temperature, Definitely, she is measuring the Relative humidity characteristics of the air.
