The correct answer is C) reduce the clearance between the assembled ring segments and shaft. Carefully filing the ends of the carbon ring packing segments ensures a tighter fit between the assembled ring and the turbine rotor shaft. This reduces the clearance between the ring segments and the shaft, which is important to prevent leakage and maintain the proper oil wedge pressure for effective lubrication. The other options are incorrect because: A) increasing the oil wedge pressure is not the primary purpose of filing the ring ends, B) reducing the ring segment end clearance is a secondary effect, not the main purpose, and D) reducing the possibility of scoring the shaft is not the main objective when fitting new carbon ring packing.