The purpose of shroud bands secured to the tips of the turbine blades is to __________.

Correct Answer: Option C — stiffen the blades to reduce vibration

Shroud bands riveted to turbine blade tips tie the blade groups together into a rigid assembly. This mechanical tying dampens resonant vibrations, stiffens the slender blades against aerodynamic excitation forces, and prevents destructive vibrational fatigue during operation.