a b c d

c

$\text{Let side of triangle is a and diameter of wire is d }$ $\text{Since total langth remains same L } = 3aN \text{ N is total number of turns}$ $\text{Self Inductance L } = \mu_0 n^2Al = \mu_0 n^2 \frac{\sqrt 3}{4} a^2dN$ $ L \propto a \text{ (Since } aN = \frac{L}{3})$ $\text{L will increase by a factor of 3.}$