Turbine disks are commonly attached to the shaft by which of the following methods?

Correct Answer: Option A — Bolted or welded.

Turbine disks are subjected to extreme centrifugal forces and thermal gradients, requiring robust attachment methods. Bolting or welding ensures the structural integrity of the rotor assembly, preventing blade migration or disk separation during high-speed operation, which is critical for maintaining the tight clearances required for efficient Brayton cycle performance.