9...................

For this case we must evaluate the following expression:
[tex]\sqrt [4] {16}[/tex]
We have by definition of properties of powers and roots that:
[tex]\sqrt [n] {a ^ m} = a ^ {\frac {m} {n}}[/tex]
On the other hand, we can rewrite the 16 as:
[tex]16 = 2 * 2 * 2 * 2 = 2 ^ 4[/tex]
So:
[tex]\sqrt [4] {16} = \sqrt [4] {2 ^ 4} = 2 ^ {\frac {4} {4}} = 2 ^ 1 = 2[/tex]
ANswer:
Option D