Labyrinth packing rings are installed on turbine diaphragms to minimize __________.

Correct Answer: Option D — interstage steam leakage along the turbine rotor

Labyrinth packing rings installed inside turbine diaphragms restrict high-pressure steam from bypassing the blading paths. By limiting interstage steam leakage along the rotating shaft through tight clearances, these rings maximize stage efficiency and overall turbine output.