The energy released in an atom bomb is obtained from?

When two deuteron nuclei fuse to form a helium nucleus,energy is released because the mass of the helium nucleus is .....

$_{1}^{2} H + _{1}^{3} H \to _{2}^{4} He + _{0}^{1} n$
If the binding energies of $_{1}^{2} H, _{1}^{3} H$ and $_{2}^{4} He$ are $a, b$ and $c$ (in $MeV$) respectively, then the energy released in the reaction is:

The best neutron moderator is:

Energy in the sun is generated mainly by

$A$ nucleus with mass number $220$ initially at rest emits an alpha particle. If the $Q$ value of the reaction is $5.5 \ MeV$,calculate the kinetic energy of the alpha particle. (in $MeV$)