🔍 Key Concepts

• Built-up vs. solid (one-piece) valves in diesel and steam engines • Why different materials might be used for the valve head, stem, or seat • How high temperature and corrosion affect exhaust valve design

💭 Think About

• Think about what "built-up" suggests in mechanical terminology: is it one solid piece or more than one piece assembled? • Which part of an exhaust valve is exposed to the highest temperature and corrosion, and how might that influence material choice? • Look at each option and ask: does this describe a one-piece valve, or a valve made from separate components put together?

✅ Before You Answer

• Verify which option clearly describes more than one component or material being combined into a single exhaust valve • Eliminate choices that only describe how many springs or a particular steel type without implying assembled parts • Focus on the option that directly indicates different materials or pieces forming the valve as a unit