The answer is D.
When something is set to a fraction of a power, it makes the base a square root. And since 81 is going to the power of 1/2 it is just squaring it. The square root of 81 is 9.
Next, anything to a negative power turns the base number into a fraction, so 3^-1 turns into 1/3^1 or 1/3.
Finally, you solve: 9/ 1/3. Fractions take the reciprocal of themselves when they are being divided so the equation is more like 9*3. And 9*3 is 27. So the answer is D, 27.
Hope this helps!