Final answer:
Resident-use hot water must be reliably controlled and not exceed a certain temperature or be less than a certain temperature at each fixture.
Step-by-step explanation:
In order to reliably control resident-use hot water, thermostatic or mixing valves are used to regulate the temperature at each fixture. The hot water should not exceed a certain temperature and should not be less than a certain temperature. The correct answer choice for the given question is (a) 150 degrees Fahrenheit and 90 degrees Fahrenheit.