Using the available references, if the dry bulb temperature is 91° and the wet bulb temperature is 87°, what is the relative humidity in a cargo hold?

Correct Answer: Option B — 85%

Entering the psychrometric chart with a dry bulb of 91°F and a wet bulb of 87°F gives a wet-bulb depression of 4°F, which equates to a relative humidity of 85% for monitoring moisture conditions.