The nucleus having the highest binding energy per nucleon is

Mass numbers of the elements $A, B, C$ and $D$ are $30, 60, 90$ and $120$ respectively. The specific binding energies of them are $5 \text{ MeV}, 8.5 \text{ MeV}, 8 \text{ MeV}$ and $7 \text{ MeV}$ respectively. In which of the following reaction$(s)$ is energy released?
$1. D \rightarrow 2B$
$2. C \rightarrow B + A$
$3. B \rightarrow 2A$

The masses of neutron, proton and deuteron in amu are $1.00893$, $1.00813$ and $2.01473$, respectively. The packing fraction of the deuteron in amu is

According to the mass-energy equivalence relation,$9 \times 10^{13} \text{ J}$ of energy can be converted into $\qquad$ maximum mass. [Speed of light $c = 3 \times 10^{8} \text{ m/s}$] (in $\text{ g}$)

$A$ nucleus of mass $M + \Delta m$ is at rest and decays into two daughter nuclei of equal mass $\frac{M}{2}$ each. The speed of light is $c$. The binding energy per nucleon for the parent nucleus is $E_1$ and that for the daughter nuclei is $E_2$. Then:

Degenerate electron pressure will not be sufficient to prevent the core collapse of a white dwarf if its mass becomes $n$ times the solar mass. The value of $n$ is: