Which particles are responsible for the flow of current in conductors?

Which of the following statements is $NOT$ true for a series combination of two resistors?

What makes the electric current flow through an electrolyte?

Find the equivalent resistance of the following circuit.

Two conducting wires of the same material,equal length,and equal diameter are connected in series. How does the heat produced by the combination of resistance change?

Two resistors of $3 \Omega$ and $6 \Omega$ are connected in parallel. The equivalent resistance $R$ is: