Answer :
When dealing with domain names and the Domain Name System (DNS), a zone file is a file that contains mappings between domain names and IP addresses and other resources, organized in the form of resource records (RRs). A zone file is used to configure the DNS server and enables it to answer queries about domain names within the zone.
Typically, the naming convention for a zone file is based on the domain it represents. Therefore, if your domain name is "practicelabs," the zone file is often named to clearly represent the domain it is associated with and to indicate its purpose as a file containing DNS records.
Option (b) practicelabs.zone is the conventional naming practice for a zone file for the domain "practicelabs". The extension ".zone" signifies that it is a zone file containing the DNS records for the domain "practicelabs". So the correct answer is:
b) practicelabs.zone