(You created a playbook on FortiAnalyzer that uses a FortiOS connector.

Comprehensive and Detailed Explanation From Exact Extract of knowledge of FortiAnalyzer 7.6 Study guide documents:

The study guide explains that FortiAnalyzer playbook tasks rely on connectors, and that the FortiOS connector will not show its available actions until FortiGate is configured with the correct automation trigger. The guide states:“For example, the FortiOS connector will be listed as soon as the first FortiGate device is added to FortiAnalyzer. However, to see the actions related to that FortiOS connector, you must enable an automation rule using the Incoming Webhook Call trigger on FortiGate.”

This is why the required FortiGate trigger type isIncoming webhook(option B): it is the specific trigger FortiOS must use so FortiAnalyzer can expose and use the FortiOS connector actions within the playbook workflow.