Answer: Option D
Explanation: The seawalls can be defined as large concrete or rock structures that are made along the sea shore so that the waves cannot reach the residential area.
The structures made are so large and strong that the waves after hitting the structures goes back and does not cause any harm towards the sea shore side.
The negative or indirect consequence of the building the seawalls is that it destroys the habitat of the shoreline animals. Habitat loss of the animals takes place.