$B$. The drift velocity is inversely proportional to the area of cross-section of given conductor.

$C$. The drift velocity does not depend on the applied potential difference to the conductor.

$D$. The drift velocity of electron is inversely proportional to the length of the conductor.

$E$. The drift velocity increases with the increase in the temperature of conductor.

Choose the correct answer from the options given below:

$(A)$ the current $I$ through the battery is $7.5 \mathrm{~mA}$

$(B)$ the potential difference across $R_{\mathrm{L}}$, is $18 \mathrm{~V}$

$(C)$ ratio of powers dissipated in $R_1$ and $R_2$ is $3$

$(D)$ if $R_1$ and $R_2$ are interchanged, magnitude of the power dissipated in $R_{\mathrm{L}}$ will decrease by a factor of $9$