Binding energy per nucleon verses mass number curve for nuclei is shown in the figure.  W, X, Y and Z are four nuclei indicated on the curve. The process that would release energy is :

Energy is released in a process when total Binding energy (B. E) of the nucleus is increased or we can say when total B.E. of products is more than the reactants. By calculation we can see that only in case of option (3), this happens. Given W→2YB. E. of reactants=120×7.5=900MeVand B.E. of products=2×(60×8.5)=1020MeV