The number of rooms in a house is a function of the number of people who live in the house.
Which of the following statements must be true?
A. The domain of the function is the population of the town.
B. If there are four rooms in the house, then there are four people living in the house.
C. The domain of the function is the number of rooms in a house.
D. The domain of the function is the number of people who live in the house.