We can apply the following properties of radicals:
[tex]\begin{gathered} \sqrt[n]{ab}=\sqrt[n]{a}\cdot\sqrt[n]{b}\Rightarrow\text{ Product property} \\ \sqrt[n]{\frac{a}{b}}=\frac{\sqrt[n]{a}}{\sqrt[n]{b}}\Rightarrow\text{ Quotient property} \end{gathered}[/tex]
Then, we have:
[tex]\begin{gathered} \text{ Apply the product property} \\ \sqrt[]{\frac{7}{8}}\cdot\sqrt[]{\frac{7}{18}}=\sqrt[]{\frac{7}{8}\cdot\frac{7}{18}} \\ \sqrt[]{\frac{7}{8}}\cdot\sqrt[]{\frac{7}{18}}=\sqrt[]{\frac{7\cdot7}{8\cdot18}} \\ \sqrt[]{\frac{7}{8}}\cdot\sqrt[]{\frac{7}{18}}=\sqrt[]{\frac{49}{144}} \\ \text{ Apply the quotient property} \\ \sqrt[]{\frac{7}{8}}\cdot\sqrt[]{\frac{7}{18}}=\frac{\sqrt[]{49}}{\sqrt[]{144}} \\ \sqrt[]{\frac{7}{8}}\cdot\sqrt[]{\frac{7}{18}}=\frac{7}{12} \end{gathered}[/tex]
Therefore, the choice that is equivalent to the given product is:
[tex]\frac{7}{12}[/tex]