The dimensions of four wires of the same material are given below. In which wire the increase in length will be maximum when the same tension is applied:

If same force is applied on four wires of same material then elongation in each wire depends on the length and diameter of the wire and given by $l\propto \frac{L}{d^2}$ and the ratio of $\frac{L}{d^2}$ is maximum for (d) option.