Final answer:
The function f(x) = 20 is a horizontal line with only one output value, 20. Therefore, its range is simply {20}, which does not match any of the provided answer choices.
Step-by-step explanation:
The range of a function represents the set of all possible output values it can produce. Considering the function f(x) = 20, which is a horizontal line, the only output value for this function is 20, regardless of the value of x within the domain 0 ≤ x ≤ 20. Thus, the range of the function is a single value, which can be represented by the set {20}. Since this set contains only one number, and does not align with any of the provided answer choices, it is necessary to review the options again or request further clarification. In conclusion, the function's range is not represented by any of the provided intervals, and the correct range for this case is merely the single value 20.