Final answer:
The correct humidistat setting in the summer is D. 30%. Relative humidity changes with temperature alterations when water vapor density is constant. Indoor humidity levels are optimally kept between 30-50% for comfort and health.
Step-by-step explanation:
The optimal humidistat control setting during the summer is generally recommended to be between 30-50% to maintain comfortable and healthy indoor humidity levels. Therefore, the correct answer to the question of what the humidistat setting should be in the summertime is D. 30%. Keeping humidity within this range helps in managing comfort, health, and preventing excessive moisture that can lead to mold growth.
In physics, the concept of relative humidity is important, especially when discussing the changes in humidity as temperatures vary. For example, if the relative humidity is 90.0% on a summer morning with a temperature of 20.0°C, it will decrease as the temperature rises to 30.0°C, provided that the water vapor density stays constant. This is because the capacity for air to hold moisture increases with temperature.