Assertion. A local telephone network is an example of circuit switched network.

Reason. In circuit switching, a complete physical connection is established between the source node and the destination node, prior to any transmission.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
When a computer initiates a telephone call, the switching equipment within the telephone system seeks out a physical copper path all the way from sender telephone to the receiver's telephone. This establishes an end-to-end connection before any data transfer. A local telephone network provides an example of a circuit-switched network.