At what distance does the minimum value of potential energy be obtained between the nucleons (in $fm$)?

$A$ particle having almost zero mass and exactly zero charge is

Consider the following statements:
$I$. All isotopes of an element have the same number of neutrons.
$II$. Only one isotope of an element can be stable and non-radioactive.
$III$. All elements have isotopes.
$IV$. All isotopes of carbon can form chemical compounds with oxygen-$16$.
Choose the correct option regarding an isotope.

The ratio of the relative strengths of strong and weak nuclear forces is

The order of magnitude of the density of a uranium nucleus is: (Given: ${m_p} = 1.67 \times 10^{-27} \ kg$)

Four statements are given ($A$ is mass number) :
$A$. The volume of a nucleus is proportional to $A^{1/3}$.
$B$. The volume of a nucleus is proportional to $A$.
$C$. The difference in mass of an atom and its nucleus is called the mass defect.
$D$. The difference in mass of a nucleus and its constituents is called the mass defect.
Choose the correct answer from the options given below :