In an atomic bomb,the energy is released due to

Assertion: Energy is released when heavy nuclei undergo fission or light nuclei undergo fusion.
Reason: For heavy nuclei,binding energy per nucleon increases with increasing $Z$,while for light nuclei,it decreases with increasing $Z$.

$A$ $\pi^0$ meson at rest decays into $2$ $\gamma$ rays: $\pi^0 \to \gamma + \gamma$. Which of the following must happen?

Imagine that a reactor converts all given mass into energy and that it operates at a power level of $10^9\, W$. The mass of the fuel consumed per hour in the reactor will be: (velocity of light,$c = 3 \times 10^8\, m/s$)

The energy of the fast neutrons emitted in a nuclear fission reactor is approximately $\qquad$ .

Which one of the following nuclear reactions is a source of energy in the sun?