In the figure, the values of currents $I_1, I_2$ and $I_3$ respectively are

Which of the following circuits is correct for verification of Ohm's law?

In a conducting region, $10^{19}$ electrons and $10^{19}$ protons move to the left, while $10^{19}$ $\alpha$-particles move to the right per second. The resulting electric current is $(e = 1.6 \times 10^{-19}\text{ C})$ _________

Current flowing through a wire decreases linearly from $10$ A to zero in $4$ s as shown in the graph. Find the total charge flowing through the wire in the given time interval.