For which of the following dependencies of drift velocity $v_d$ on electric field $E$ is Ohm's law obeyed?

Drift speed $(v_d)$ varies with the intensity of the electric field $(E)$ as per the relation:

The relationship between the electric field $E$ and the current density $J$ is given by:

The drift velocity of electrons in a conducting wire connected to a cell is $V_{d}$. If the length of the wire is doubled and the area of cross-section is halved,then the drift velocity of electrons becomes:

Charge passing through a conductor of cross-section area $A=0.3 \,m^2$ is given by $q=3 t^2+5 t+2$ in coulomb,where $t$ is in second. What is the value of drift velocity at $t=2 \,s$ ? (Given,$n=2 \times 10^{25} / m^3$ )

In the given figure,a battery of emf $E$ is connected across a conductor $PQ$ of length $L$ and different area of cross-sections having radii $r_{1}$ and $r_{2}$ $(r_{2} < r_{1})$. Choose the correct option as one moves from $P$ to $Q$: