Electric current is a _ _ _ _ _ _.
A. Scalar quantity
B. vector quantity
C. vector quantity when it is due to the flow of positive charges
D. vector quantity when it is due to electrons.

Hint: Current is the flow of charges per unit time. The direction of current in a circuit is opposite to the direction of flow of electrons. Current is operated as scalar and not as vectors.

Complete step-by-step answer:
When there is a flow of charge through a material, we say there is current in the material. Current is defined as the amount charges that flow in one unit of time. We can also say that current is the rate of flow of charges with respect to time.
Suppose q amount of charges flow in a given amount of time t. Then the average current is simply the amount of charge flown divided by the time taken i.e. $i=\dfrac{q}{t}$.
Current is a scalar quantity. Meaning it has a magnitude but no specific direction.
However, when there is a flow of charges, the direction of the current in the circuit is a particular direction. This is due the difference in potential at different points.
The battery or cell attached in the circuit creates a potential across in its terminal. When there is a potential difference between two points, charges begin to flow between the points. The direction of current depends on the potentials at the points. Meaning, current always flows from higher potential to a lower potential i.e. opposite to the direction of flow of electrons.
Current is a scalar quantity because different currents are added like scalars and not vectors.
Consider the current in the junction given in the figure. Here, two currents ${{i}_{1}}$ and ${{i}_{2}}$ result into current ${{i}_{3}}$. Here, ${{i}_{3}}={{i}_{1}}+{{i}_{2}}$. Hence, current is a scalar quantity.
Hence, electric current is a scalar quantity.

Note: If the flow of charges is uniform for the entire time, then the current is constant and at any instant of time it will equal to $i=\dfrac{q}{t}$.
If the flow current is not uniform, then the current is not constant and changes along with time. At any instant of time, the current will be equal to $i=\dfrac{dq}{dt}$.