Answer
$\color{blue}{2}$
Work Step by Step
RECALL:
(1) $a^{1/n} = \sqrt[n]{a}$
(2) If $a \gt 0$, then $\sqrt[n]{a^n} = a$
Use rule (1) above to obtain:
$16^{1/4} = \sqrt[4]{16}$
Since $16=2^4$, then the expression above is equivalent to:
$=\sqrt[4]{2^4}$
Use rule (2) above to simplify and have:
$\sqrt[4]{2^4}=\color{blue}{2}$