Answer:
A. basal sliding is the correct answer.
Explanation:
basal sliding phenomenon helps glaciers move down the valleys of the southern Alps.
Basal sliding is the action of the glacier moving down across the bed because of the melting of water below the ice moving as the lubricant.
Basal sliding depends on the temperature of the region, the movement of the glacier, roughness of the bed, the melting of water from the glacier, and the size of the glaciers.
