For the decay of a nucleus,which of the following is $NOT$ a possible reason?

What is mass defect? Write down its formula.

Binding energy per nucleon of a fixed nucleus $X^A$ is $8 \ MeV$. It absorbs a neutron moving with kinetic energy $2 \ MeV$ and converts into $Y$,emitting two photons of energy $1 \ MeV$ and $4 \ MeV$ respectively one after the other. The binding energy per nucleon of $Y$ (in $MeV$) is:

If the binding energy per nucleon for $\,_3^7\,Li\,\,$ and $\,_2^4\,\,He$ are $5.60 \,MeV$ and $7.06 \,MeV$ respectively, then the energy of the proton in the reaction $p\,\, + \,\,_3^7\,\,Li\,\, \to \,\,2\,_2^4\,\,He$ must be .......... $MeV$.

Explain the following forms and principles of energy:
$(a)$ The Equivalence of Mass and Energy
$(b)$ Nuclear Energy
$(c)$ The Principle of Conservation of Energy

The binding energy per nucleon for a deuteron $(_{1}^{2}H)$ and an $\alpha -$ particle $(_{2}^{4}He)$ are $x_1$ and $x_2$ respectively. The energy $(Q)$ released in the reaction $_{1}^{2}H + {}_{1}^{2}H \to {}_{2}^{4}He + Q$ is