Answer
The torque about the origin is $~~0$
Work Step by Step
We can find the angular momentum about the origin:
$L = rmv~sin~\phi$
Since the car moves along the x axis, the angle $\phi$ between the displacement vector and the velocity vector is either $\phi = 0^{\circ}$ or $\phi = 180^{\circ}$
Then $sin~\phi = 0$ and it follows that $L = 0$
The angular momentum about the origin is $~~0$ fro all values of $t$
The torque is equal to the change in angular momentum.
Since the change in angular momentum is $0$ for all values of $t$, the torque is $0$ for all values of $t$
