Final answer:
Without the specific function, we cannot determine the exact domain. The domain is all possible x-values for which the function is defined, and based on related examples, it's likely to be [0, +∞) for positive real numbers.
Step-by-step explanation:
The question does not provide the specific function in question. However, the domain of a function refers to all possible input values (x-values) for which the function is defined. From the information given in Practice Test 2 Solutions, particularly when considering a function like f(x) for a real number in the range 0 ≤ x ≤ 20, it implies that the domain would be all real numbers within that closed interval, therefore, [0, +∞) or in this limited case, [0, 20]. To answer the student's multiple-choice question accurately, we would need the specific function they are inquiring about. Nonetheless, answer choice (c) [0, +∞) is the closest match to the concept of a function having a domain where x is zero or a positive real number.