The cell membrane allows substances to enter and leave the cell and gives the cell structure.
Answer:
Source of current, force and pathway.
Explanation:
Source of current, force and pathway are the three important things needed or responsible for the current flow. A supply of electric charges (electrons) which is provided by the electric source, force of push to move the charges through the circuit and a pathway on which current flows. Without these three things, flow of current is impossible. so we can say that the situation in which all these three things are present will allow the current to flow in the circuit.