Explanation:

To find the radius of the cylinder, we can use the volume formula for a cylinder:

$$ \text{Volume} = \pi \times r^2 \times h $$ where \( h = 6 \text{ cm} \) and \(\text{Volume} = 231 \text{ cm}^3\).

- Rearrange the formula to solve for the radius \( r \):

$$ r^2 = \frac{\text{Volume}}{\pi \times h} $$

$$ r^2 = \frac{231}{\pi \times 6} $$

$$ r^2 = \frac{231}{18.8496} \approx 12.25 $$

- Taking the square root:

$$ r \approx 3.5 $$

- The correct option is: 4. 3.5 cm

- Option 1 (35 cm), Option 2 (21 cm), and Option 3 (2.1 cm) do not satisfy the volume equation.