How is ChatGPT integrated with other systems? Select anyone? 1. LLMs. 2. None of the listed options. 3. API Key. 4. NLP.

The best option that relates to the integration of ChatGPT with other systems is **3. API Key**. ChatGPT can be integrated into various applications and systems using an API, which requires an API key for authentication. This allows developers to incorporate ChatGPT's capabilities into their own platforms, such as chatbots, customer support systems, and other applications, leveraging the language model's functionalities.