The correct answer is A. plucking.
Plucking is the process of particle detachment by moving glacial ice. It occurs when the ice freezes to a rock or other particle and then the ice moves, pulling the particle loose. Plucking is a major process in the formation of glacial erratics, which are large boulders that are found far from their original source.
Abrasion is the process of rock erosion by friction between rock particles and a moving surface. It is a major process in the formation of glacial striations, which are long, parallel scratches that are found on the surface of rocks that have been eroded by glaciers.
Sc scouring is the process of rock erosion by the impact of moving particles. It is a major process in the formation of glacial potholes, which are deep, round holes that are found in the bedrock beneath glaciers.
None of the above is not the correct answer because it does not describe a process of particle detachment by moving glacial ice.