In the scenario you described, an administrator has created a firewall address object used in multiple policy packages for multiple FortiGate devices within an Administrative Domain (ADOM) on FortiManager. The question concerns the display of this object's IP/netmask in FortiManager after installation, assuming no per-device mapping is specified.
Given the screenshot and the description of the situation, the answer is **C. 192.168.1.0/24**. When you create a firewall address object in FortiManager without specifying per-device mapping, FortiManager uses the generic settings of the object as defined. In the screenshot, the IP/Netmask is set to 192.168.1.0/255.255.255.0, and since there is no per-device variation defined or required in your query, this setting remains as shown in the object's configuration.