Choose the correct option: 

A cube has a total surface area of 54 cm². The side length of a cube is ____ cm.

Given,

the total surface area of a cube is 54cm².

the total surface area of a cube = 6 (side)²

$$\begin{gathered} 6{\left(\mathrm{side}\right)}^2=54 \\ \Rightarrow {\mathrm{side}}^2=9 \\ \Rightarrow \mathrm{side}=3 \mathrm{cm} \end{gathered}$$

Therefore, the side length of a cube = 3 cm