Final answer:
The domain of a function is the set of all input values for which the function is defined. For a horizontal line graphed between x = 0 and x = 20, the domain would be 0 ≤ x ≤ 20. None of the provided options match this domain correctly.
Step-by-step explanation:
The domain of a function refers to the set of all possible input values (usually x values) for which the function is defined. In the context of graphed functions, it is represented by the range of x values along the horizontal axis that correspond to points on the graph.
In the situation given, if the graph of f(x) is a horizontal line between x = 0 and x = 20, then the domain of this function is the set of all real numbers between and including these two values. Hence, the correct domain for the function would be: 0 ≤ x ≤ 20.
Looking at the given options, none of them directly match this interval. However, option D: -9 ≤ X ≤ 5 seems to refer to a subset of real numbers much like a domain, yet it does not correctly describe the domain of the function in question.