When crustal plates move together and compress the rock into a series of waves, this process is known as? a> deposition b> faulting c> folding d> weathering

This process is known as c>folding.

The occurrence of folding happens when crustal plates move together under the compressional force, causing the rocks to fold into a series of waves. In some cases folding might be small scaled and not significant, while in large scaled folding features like the fold mountains will be formed.

Let's look into the rest of the answer one by one:

a>deposition

Deposition is a movement that occurs under gravity, where the small particles of rock or soil is deposited on the surface. It could occur when the current of water is gentle, or when rock weathers and the smaller particles fall off. A long term deposition could cause the formation of sedimentary rock when particles accumulate.

b> faulting

Faulting can occur under compressional force, shear force or tensional force. When the compressional force is so strong that overthrust occur, the rock might break under the pressure and cause faulting. While shear stress and tensional force will pull the rock apart and cause faulting. Some examples caused by faulting is rift valley.

d> weathering

Weathering is the break down or dissolving of rock under physical factors or chemical factors. For example, under the difference of temperature, the rock will contract and expand at an alternate rate and break apart. An example for chemical factors is when the rock that include dissolvable materials dissolved under acid or water.

Therefore the answer is  c>folding.

Hope it helps!