This question is a describe question so you do not have to explain how these processes work, you should point out similarities and differences between the three processes. You should write five clear points to gain full marks. It is easiest to break the question down into the three processes and then comment on how they differ from one another. For example:
These are all methods of erosion which wear away rock and cliff on the coastline. Abrasion is where pebbles and small material in the sea grind along a rock platform. It is gradual and has a similar action to sandpaper. Over time, the rock becomes smooth and worn. Solution is when sea water or chemicals in the sea can dissolve rock. For example limestone. Attrition is where material the sea is carrying knocks and rubs against each other. This breaks it into smaller pieces and they become more smooth and rounded.
Abrasion acts mainly on the cliff face, whereas attrition usually happens with material that is already broken off, on the sea bed (pebbles). Solution is similar to both because it can act directly act on the cliff face and the sea bed. Attrition and abrasion are similar because they both involve material rubbing against each other and scraping away. In contrast, solution doesn't use other sediment to break down the rock.