The correct answer is (d), all the above.
Explanation:
Opposition to large dam construction arises from a combination of social, economic, and environmental concerns.
Social reasons:
Dams often displace local communities, forcibly relocating them from their homes and traditional lands. This can lead to social disruption, loss of cultural heritage, and conflict over compensation.
Economic reasons:
While dams can generate hydropower, the construction costs are high. The benefits of the generated electricity may not always outweigh the initial investment and ongoing maintenance costs. Additionally, dams can sometimes lead to decreased economic activity downstream due to changes in river flow and sediment deposition.
Environmental reasons:
Dams significantly alter river ecosystems. They can lead to the loss of biodiversity, habitat fragmentation, changes in water temperature and flow, and increased pollution. Dams can also contribute to flooding upstream and downstream.
Therefore, all options (a), (b), and (c) are correct.