Waves cause erosion through the processes of and abrasion.
a. chemical weathering
b. impact

B. impact

Waves cause erosion through the processes of IMPACT and abrasion.

Erotion is defined as a surface process action wherein soil, rock, and dissolved materials are removed from one location and transported to another location through water flow or wind flow.

Waves causes erosion because constant wave impact on rocky and sandy shores will slowly break it down into small pieces which will be transported to another part of the Earth. 

Answerseafloor spreading;