The export rules for client specifications must typically define the network segment from which clients are allowed to access the exported data. The option with '192.168.100.0/16' specifies a range within a private IP address block, making it a valid client specification. The option '0.0.0.0/0' represents the default route for all IPv4 addresses, essentially allowing access from any IP, which is another valid form of specification for all clients. Thus, A and D are correct.