The correct option is OpenAI Codex model.

GitHub Copilot was built in partnership with OpenAI and Codex provided the code understanding and generation that produced inline suggestions in editors. It translated natural language into code and completed functions across many languages which is exactly the behavior users see in IDEs. OpenAI later retired Codex and Copilot now uses newer GPT models, yet historically the IDE integration that this question targets was powered by Codex.

Azure Cognitive Services is a collection of prebuilt AI APIs for tasks like vision and speech and it is not the specific model that generated Copilot suggestions in IDEs. Copilot relied on OpenAI models rather than Azure Cognitive Services.

Vertex AI Codey is a Google service for code generation on Google Cloud and it does not power GitHub Copilot in IDEs.

Google BERT is a language representation model aimed at understanding text and it is not designed for code completion in IDEs and is not used by Copilot.

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