the erosion of land along the coastline the buildup of dunes along the coast over time the new construction of buildings along the coastline the buildup of organic material from oil rigs along the coast
I gave my students this multiple choice question: Which of these serve as protective barriers along coastlines and are often destroyed when hit by a strong hurricane?

Only one answer is correct among these 4 choices:
- the erosion of land along the coastline
- the buildup of dunes along the coast over time
- the new construction of buildings along the coastline
- the buildup of organic material from oil rigs along the coast

Could you tell me which one is correct?

the buildup of dunes along the coast over time