Carbon Is tetravalent. This means that at any particular point in time, the number of bonds carbon can form at a particular time is 4. Now in this particular question, there is already a double bond between the two carbon atoms. This means that each of the carbon atom has the chance to fulfill it tetra valency by attaching just two bonds to itself.
Hence, to complete the property of its tetra valency, two more bonds needed to be added to the two carbon atoms
These are usually copper wires with no insulation. They make the path through which the electricity flows. One piece of the wire connects the current from the power source (cell) to the load
