To find the cube root of 81, we can express it as:
\[ \sqrt[3]{81} \]
We know that \(81\) can be expressed as \(3^4\) since \(3^4 = 81\). Therefore, we can rewrite the cube root as:
\[ \sqrt[3]{81} = \sqrt[3]{3^4} = 3^{4/3} \]
This can be simplified to:
\[ 3^{4/3} = 3^{1 + 1/3} = 3 \cdot 3^{1/3} \]
Hence, the cube root of 81 is \(3 \cdot \sqrt[3]{3}\).
However, since we are looking for a numerical approximation or a simple form, we don't have a whole number for \( \sqrt[3]{81} \), so among the options you provided, none seem to match.
Nonetheless, \(\sqrt[3]{81} \approx 4.326\), which isn't included in the options. The closest simplified form for any comparison is still \(3 \cdot \sqrt[3]{3}\).
If we strictly follow through with the options given, they don't provide the correct representation or the closest numerical value based on the standard cube root operations. Please recheck the provided options.