Which of the following items should NOT be used to mark turbine engine components exposed to high temperatures?

In the context of marking turbine engine components that are exposed to high temperatures, it's essential to choose materials that withstand those conditions without degrading or introducing contaminants. Wax or grease pencils are not suitable because they can melt or break down when subjected to high temperatures, potentially leading to the release of harmful substances. This can adversely impact the performance, safety, and integrity of the engine components.

On the other hand, commercial felt tip markers and layout dyes are generally designed to resist heat to some degree, making them more appropriate for high-temperature applications. Chalk can also be used, as it tends to withstand heat without causing damage or contamination. Therefore, while wax or grease pencil may seem convenient for marking, they should be avoided in environments where high temperatures are a factor due to their properties that can compromise engine safety and functionality.