Answer:
The function g(x) = √(x - 3) is defined for all real numbers x such that x - 3 ≥ 0, since the square root of a non-negative number is a real number.
Solving for x, we have:
x - 3 ≥ 0
x ≥ 3
Therefore, the domain of the function is D: [3, ∞).
Since the square root of a non-negative number is always non-negative, the range of the function is R: [0, ∞).
Therefore, the correct answer is: A. D: [3, ∞) and R: [0, ∞).