Which of the following is the most stable?

Two sources of equal emf $E$ are connected in series to an external resistance $R$. The internal resistances of the two sources are $R_1$ and $R_2$ $(R_2 > R_1)$. If the potential difference across the source having internal resistance $R_2$ is zero,then the value of $R$ is:

When a big drop of water is formed from $n$ small drops of water,the energy loss is $3E$,where $E$ is the energy of the bigger drop. If $R$ is the radius of the bigger drop and $r$ is the radius of the smaller drop,then the number of smaller drops $(n)$ is:

Which of the following was isolated and identified by Skoog and Miller?

In the circuit shown,a potential difference of $60\,V$ is applied across $AB$. The potential difference between the points $M$ and $N$ is.....$V$

$I.$ $DNA$ being a hydrophilic molecule cannot pass through cell membranes.
$II.$ The bacteria should be made competent to accept the $DNA$ molecule.
The correct option regarding the above statements is: