The correct answer is A. solution.
Solution is a process that involves the eroded material being dissolved and carried along in water as individual ions. This is the most common form of erosion, and it is responsible for the transport of a large amount of sediment.
Suspension is a process that involves the eroded material being carried along in water as small particles. These particles are too large to be dissolved, but they are small enough to remain suspended in the water.
Saltation is a process that involves the eroded material being bounced along the surface of the water. This process is most common in turbulent water, and it is responsible for the transport of a small amount of sediment.
Traction is a process that involves the eroded material being dragged along the surface of the water. This process is most common in slow-moving water, and it is responsible for the transport of a small amount of sediment.