Where do you store the OpenAI API key as a best prctice? select anyone? 1. CSV file. 2. Environment variable. 3. Text file. 4. String variable.

The best practice for storing an OpenAI API key among the options you've provided would be **2. Environment variable**. Using environment variables helps keep sensitive information like API keys secure and out of your source code, reducing the risk of accidental exposure in version control systems.