Correct option is (b) Loopback address
Explanation: In subcategories of reserved address in IPv6, address that is used by a host to test itself without going into network is called loop back address. IPv6 loopback address is 0000:0000:0000:0000:0000:0000:0000:0001. IPv4 loopback address is 127.0.0.1. It’s a reserved address.