🔍 Key Concepts

• Think about where a colored marking compound might be useful in engine or machinery work • Compare the purposes of water treatment chemicals vs lubricating oil additives vs inspection compounds • Recall how engineers check contact areas between two metal surfaces (like seats and discs)

💭 Think About

• Which of these options actually requires a visible color transfer to show fit or contact? • Do cooling or boiler water treatment chemicals need to leave a precise trace on metal surfaces, or are they mainly for controlling scale/corrosion inside systems? • When would an engineer want to lightly coat a surface with a blue pigment and then press parts together?

✅ Before You Answer

• Identify which option involves a visual inspection rather than chemical conditioning of fluids • Eliminate options that deal with continuous system treatment (running systems) instead of spot-checking mechanical fits • Ask yourself: where have you seen or heard of mechanics using a blue dye/compound during overhaul or maintenance?