(N/A) The flow of electric current in a conductor is due to the motion of electrons. These electrons are not completely free to move; they collide with the atoms and ions of the conductor as they drift. These collisions and the electrostatic attraction exerted by the atoms hinder the motion of electrons,which manifests as resistance.
$(b)$ Conductor: $A$ material that allows electric current to flow through it easily due to the presence of free electrons.
Resistor: $A$ component or conductor that has a specific,significant amount of resistance,used to control or limit the flow of current in a circuit.
Resistance: It is the inherent property of a material by virtue of which it opposes the flow of electric current through it.