Which is also known as a connectionless protocol for a packet-switching network that uses the Datagram approach?

IPV4 (Internet Protocol version 4) is a connectionless protocol used in packet-switching networks. It is the most widely used version of the Internet Protocol. IPV4 uses the Datagram approach, where data is divided into small packets, each packet is individually routed to its destination, and packets can take different paths to reach the destination. The packets are then reassembled at the destination to form the complete data.

IPV5 and IPV6 are also Internet Protocol versions, but they are not specifically known for being connectionless or using the Datagram approach. Therefore, option B, IPV4, is the correct choice in this context.