Which one of the following pesticides is banned now-a-days?

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 $k > 1$.

If in a $\triangle ABC$,$r_3 = r_1 + r_2 + r$,then $\angle A + \angle B$ is equal to (in $^{\circ}$)

When a current of $2\, A$ flows in a battery from negative to positive terminal, the potential difference across it is $12\, V$. If a current of $3\, A$ flows in the opposite direction, the potential difference across the terminals of the battery is $15\, V$. The $emf$ of the battery is ............... $V$.

Which one of the following statements is correct with respect to basic character?

Arrange $Ce^{+3}, La^{+3}, Pm^{+3}$ and $Yb^{+3}$ in increasing order of their ionic radii.