Which of the following is equal to? ( in picture)

Hence, option D is correct.
[tex]\dashrightarrow \sf \sqrt{\sqrt[3]{2}}[/tex]
apply radical rule
[tex]\dashrightarrow \sf \left(2^{\dfrac{1}{3}}\right)^{\dfrac{1}{2}}[/tex]
apply exponent rule
[tex]\dashrightarrow \ \sf 2^{\dfrac{1}{6}}[/tex]