Higher sea level will mean less space at the beach. A combination of stronger storms and sea level rise could increase the rate of erosion along the coast, and some beaches could disappear altogether. What can people do about it?
People already add sand to certain beaches to replace sand that has washed away. In the future, people might have to replenish beach sand more often, but this will cost more money. In other places, people might choose to build sea walls or other structures to protect the shore from erosion. Ideally, these projects will be planned carefully to prevent them from damaging important habitats for plants and animals.

Based on the excerpt, what conclusion can be drawn about sea walls?
If they are well planned, they will most likely be too expensive.
If they are well planned, they can replace sand that has been washed away.
If they are not well planned, they can damage other structures.
If they are not well planned, they can damage places with sea life.