To simplify the expression, we can rewrite each term using their prime factorization:

- 81 = 3^4, so 81\(^{\frac{-3}{4}}\) = (3^4)\(^{\frac{-3}{4}}\) = 3\(^{-3}\)

- 25 = 5^2, so 25\(^{\frac{1}{2}}\) = (5^2)\(^{\frac{1}{2}}\) = 5

- 243 = 3^5, so 243\(^{\frac{2}{5}}\) = (3^5)\(^{\frac{2}{5}}\) = 3^2

Substituting these values into the original expression, we get:

81\(^{\frac{-3}{4}}\) x 25\(^{\frac{1}{2}}\) x 243\(^{\frac{2}{5}}\) = 3\(^{-3}\) x 5 x 3^2

= (3\(^{-3}\) x 3^2) x 5

= 3\(^{-1}\) x 5

= \(\frac{1}{3}\) x 5

= \(\frac{5}{3}\)

So the simplified expression is \(\frac{5}{3}\), which corresponds to option D. Is there anything else you would like to know?