When wet bulb and dry bulb temperatures are the same, this indicates a relative humidity of _____?

When the wet bulb and dry bulb temperatures are equal, it signifies that the air is completely saturated with water vapor, meaning it holds the maximum amount of moisture it can at that temperature. This condition corresponds to a relative humidity of 100%.

Relative humidity is a measure of the current amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature. When both temperatures are the same, there is no difference in the ability of the air to hold moisture—indicating that it is fully loaded with water vapor. Thus, the correct answer reflects the condition of maximum humidity, which is 100%.