(a)
Statement 1: Difference in energies of the charge is 0 since energies in both initial and final states are 0. So work done too is 0.
Statement 2 : Net Electric potential at Origin is \frac{+q}{4\pi \epsilon _0\; d}+\frac{-q}{4\pi \epsilon _0\; d}
I.e 0
So statement 2 perfectly explains statement 1