[tex] \left( 16 x^8 y^{-12} \right)^{\frac 1 2} = 16^{\frac 1 2} (x^8)^{\frac 1 2} (y^{-12})^{\frac 1 2} = 4 x^4 y^{-6} = \dfrac{4 x^4}{y^6}[/tex]
Third choice
