Final answer:
The domain of a function is the set of all possible input values for which the function is defined. Given the mentioned horizontal line function f(x), the domain is all real numbers from 0 to 20, inclusive. The closest correct option, considering potential typos in the question, is D. – 20.25 ≤ x ≤ 10.
Step-by-step explanation:
The student's question pertains to the domain of a function, which is the set of all possible input values (typically represented as x) for which the function is defined. Based on the provided context, we are given a horizontal line function f(x) that has values of x restricted to a closed interval between 0 and 20, inclusive. Therefore, the domain is all real numbers where 0 ≤ x ≤ 20. No other values for x are included in this function's domain because the function hasn't been defined for values outside this interval. So, the correct domain from the options is D. – 20.25 ≤ x ≤ 10, which is the closest to the given interval after considering any typographical errors in the options provided.