Answer :
[tex]\begin{gathered} \frac{6ab}{(a^0b^2)^4}=\frac{6ab}{(1\cdot b^2)^4} \\ =\frac{6ab}{(b^2)^4} \\ =\frac{6ab}{b^8} \\ =\frac{6a}{b^7} \end{gathered}[/tex]
Therefore the answer is the first one.