Statement 1 : Hydrogen nucleus combines to form helium then energy is released.

Statement 2 : Binding energy / nucleon of He is greater than hydrogen.

A nuclear reaction in which two lighter nuclei are fused together to form a heavier nuclei is called nuclear fusion. In such a process, more stable nuclei come into existence and binding energy per nucleon increases. Fusion reactions are highly exothermic because of loss of mass during fusion. e.g.

${ }_1^{2}H{+}_1^{2}H\to {}_2^{4}He+24.9MeV.$