To simplify the radical expression \(\sqrt{170}\), we can look for perfect square factors of 170.
The prime factorization of 170 is: \[ 170 = 2 \times 5 \times 17 \] None of the factors (2, 5, and 17) are perfect squares, so there are no perfect square factors to take out of the square root.
Therefore, \(\sqrt{170}\) cannot be simplified further in terms of whole numbers or simpler radicals.
Thus, the correct answer is: A. this radical expression is already fully simplified.