Read this excerpt from "A Student's Guide to Global Climate Change." Based on the excerpt, what conclusion can be drawn about protective barriers? Climate change poses risks for cities near the ocean. Places like Miami; New York City, New Orleans; and Venice, Italy, could flood more often or more severely if sea level continues to rise. If that happens, many people will lose their homes and businesses.
What can people do about it? Coastal cities can prepare for climate change by protecting or restoring natural shoreline buffers like sand dunes and wetlands, improving storm drainage systems, and building protective barriers where necessary.

A. They should be built along coastal communities.
B. They should be built where natural barriers are missing.
C. They are the same as natural barriers.
D. They are usually unnecessary along shorelines.