Final answer:
The CLI of a Fortinet device can be accessed directly through the console port using a console cable and terminal emulation software.
Step-by-step explanation:
The Command Line Interface (CLI) of a Fortinet device can be accessed through various methods, but the most direct way is via the console port. Devices such as FortiGate firewalls have a console port, which can be used to connect a computer directly to the device using a console cable. Once connected, terminal emulation software, such as PuTTY or Tera Term, can be used to interface with the CLI. While options like a FortiManager or Fabric Connector may allow management of multiple devices or integration with other systems, and the Web GUI provides a graphical user interface for configuration, they do not serve as primary methods to access the CLI. Therefore, the correct answer is (d) Console port.