The best answer for what's one indirect consequence of building seawalls
D. The shoreline habitat is destroyed through loss of sand.
Explanation: The seawalls are structure build near the seashore to prevent the coastal erosion and other damages that is caused due to the wave action.
The structures are made of concrete and usually very massive structure as they are build to restrict the effect of wave action.
The negative consequence associated with building seawall is that it disturbs the habitat of the shoreline animals.