Explanation:

- The volume of the metallic sphere is given by the formula: \( V = \frac{4}{3} \pi r^3 \). With a radius of 21.6 cm, its volume can be calculated.

- The sphere is melted to form a wire, and conservation of volume states: Volume of sphere = Volume of wire.

- The volume of the wire is given by: \( V = \pi r^2 h \), where \( r \) is the radius of the wire and \( h \) is the length of the wire, which is 259.2 m (or 25920 cm for consistency).

- Calculate: Set the two volume equations equal and solve for the wire's radius.

- Calculation reveals that the radius of the wire is approximately 0.72 cm.

- Correct Answer: Option 4 - 0.72 cm