Which of the following wave actions is a process of erosion

Hydraulic action is a process of wave erosion. It occurs when waves crash against rock surfaces and force air into cracks and joints in the rock. The repeated compression and expansion of trapped air exerts enormous pressure, gradually weakening and breaking apart the rock. This is one of the primary ways waves erode coastlines, forming features such as cliffs, caves, arches, and stacks.

The other options are all processes of transportation, not erosion:

• Saltation is the bouncing movement of particles along a surface, carried intermittently by wind or water.
• Traction involves large, heavy particles being rolled or dragged along the bed by the force of moving water or wind.
• Suspension is the carrying of fine, light particles within the body of moving water or air.

The key distinction is that erosion refers to the wearing away and removal of rock material, while transportation refers to how already-eroded material is moved from one place to another.