How do you check if Karel is not facing a particular direction?

The option that involves using the NOT operator with the facing direction check is correct because it directly addresses the logic needed to determine Karel's orientation. In programming, the NOT operator is often used to invert a condition. For instance, if there's a built-in function to check if Karel is facing a specific direction, applying the NOT operator would allow you to confirm if he is facing any direction other than the one specified.

This approach is efficient and aligns with programming principles, allowing for concise code and logical decision-making. It also ensures that the check is performed programmatically rather than relying on manual observation or adjustments, which could lead to errors or inconsistencies.

Other options might involve indirect or less effective methods, such as visually checking Karel's surroundings or manually changing his direction, which does not leverage programming logic effectively for decision-making tasks.