The ratio of the specific charge of an $\alpha$-particle to that of a proton is

Mark the correct statement.

The force between two protons is the same as the force between a proton and a neutron. The nature of the force is:

If the radius of $_{13}^{27}Al$ is $3.6 \ fm$,then the radius of the $_{52}^{125}Te$ nucleus will be ........ $fm$.

The atomic weight of boron is $10.81$ and it has two isotopes $_5B^{10}$ and $_5B^{11}$. The ratio of $_5B^{10} : _5B^{11}$ in nature is:

$(a)$ Two stable isotopes of lithium $_{3}^{6} Li$ and $_{3}^{7} Li$ have respective abundances of $7.5 \%$ and $92.5 \%$. These isotopes have masses $6.01512 \; u$ and $7.01600 \; u$,respectively. Find the atomic mass of lithium.
$(b)$ Boron has two stable isotopes,$_{5}^{10} B$ and $_{5}^{11} B$. Their respective masses are $10.01294 \; u$ and $11.00931 \; u$,and the atomic mass of boron is $10.811 \; u$. Find the abundances of $_{5}^{10} B$ and $_{5}^{11} B$.