In a twin-spool turbine, secondary air is most essential for cooling in what section?

Correct Answer: Option B — HP Turbine

High-pressure turbine blades operate in the hottest gas path immediately downstream of the combustor. Secondary air, typically bled from the compressor, is essential for film and convective cooling of these blades to prevent metallurgical failure, as gas temperatures frequently exceed the melting point of the turbine alloys.