Users of a Copilot Studio agent are reporting that when they ask questions the agent cannot answer, they receive a generic 'I'm sorry, I don't understand' message that doesn't provide any guidance on what the agent can help with. The developer wants to improve this experience. What should the developer modify?

Copilot Studio includes several system topics that control core agent behaviors. The 'Fallback' system topic fires whenever no other topic's trigger phrases match the user's input. It is fully customizable.

Option B is correct. By editing the Fallback system topic, the developer can replace the generic message with a helpful, branded experience: list what the agent can help with, offer alternative contact options, or trigger an escalation to a live agent via the 'Transfer to Agent' node. This is a high-impact customization that significantly improves user experience for out-of-scope queries.

Option A is incorrect. Creating a 'Help' topic with trigger phrases doesn't address the fallback scenario — users who fall through to Fallback have already failed to match any topic. The Fallback topic needs to handle unrecognized inputs, and trigger-phrase-based topics cannot cover all possible unrecognized inputs.

Option C is incorrect. Adding more trigger phrases to existing topics reduces the fallback rate but doesn't fix what happens when users do fall back. Both improvements are valuable, but the question specifically asks about improving the fallback experience.

Option D is incorrect as a complete solution. Enabling generative answers may handle some fallback cases, but it requires a configured knowledge source and may still fail for off-topic questions. Modifying the Fallback topic is the correct answer for controlling the experience when the agent genuinely cannot help.