Here,s why the other options are incorrect:
A). Create a new VNIC resource and specify the required IP range during attachment to an instance: This option only assigns the specific IPs needed for that instance, not a separate reserved block. You can,t reserve IPs through VNIC attachment.B. Use the oci network ip-reservation create command with the --private-ip-reservation-id flag: This command is used to create a named reservation for a specific IP address, not a contiguous block of 10 addresses.D. Modify the subnet CIDR block to accommodate the additional IPs and update the associated route tables: Modifying the subnet CIDR block is not recommended for reserving a small number of addresses as it affects all other resources in the subnet and requires updating route tables, potentially introducing errors.Option C allows you to directly select "Reserve IP addresses" within the subnet details and specify the desired number and range. This ensures the addresses are contiguous and reserved for your application without impacting other resources in the subnet.