Which one of the following items gives its correct total number?

Consider the following statements $A$ and $B$. Identify the correct choice in the given answer.
$A$. $p-n, p-p$ and $n-n$ forces between nucleons are not equal and charge dependent.
$B$. In a nuclear reactor,the fission reaction will be in an accelerating state if the value of the neutron reproduction factor $k > 1$.

Which of the following statements is consistent with halophiles?

$Assertion:$ The total translational kinetic energy of all the molecules of a given mass of an ideal gas is $1.5$ times the product of its pressure and its volume.
$Reason:$ The molecules of a gas collide with each other and the velocities of the molecules change due to the collision.

If $y = \frac{e^x \log x}{x^2}$,then $\frac{dy}{dx} = $

$\lim _{x \rightarrow 0} \frac{\sqrt{1+x^2}-\sqrt{1-x+x^2}}{3^x-1}$ is equal to