"GitHub Copilot has a duplication detection filter that checks suggestions of about 150 characters or longer against public code on GitHub. If a match is found, the suggestion is blocked if you have configured blocking." This clearly defines the purpose as preventing Copilot from suggesting verbatim code found publicly.
References: GitHub Copilot duplication detection documentation.

"If excluded content is referenced by non-excluded code, such as through function calls, Copilot may still use that reference context." This confirms that excluded content can indirectly appear if referenced elsewhere.
References: GitHub Copilot content exclusions limitations documentation.

The duplication detection filter can be configured at the organization level to prevent GitHub Copilot from suggesting publicly available code snippets.

"On GitHub Mobile, you can use emojis in the Copilot Chat interface to provide quick feedback on the responses." This makes option A correct.
References: GitHub Copilot Mobile documentation.

GitHub Copilot Chat combines its training data, code from user repositories, and external sources like Bing to generate comprehensive and relevant responses to coding questions.
Reference: GitHub Copilot Chat documentation on data sources.