Which of the following is a negative externality of creating a hydroelectric dam on a major river?

a. lakes for tourists

b. energy creation

c. improved flood control

d. environmental impact

The one that regarded as a negative externality of creating a hydroelectric dam on a major river is: D. Environmental impact

Installing Hydroelectric dam in the major river will change the chemical composition of the ecosystem in that area.
This will heavily affect the biodiversity in that ecosystem 

During the paleolithic, hominins grouped together in small societies such as bands, and subsisted by gathering  plants  and fishing, hunting or scavenging wild  animals. the paleolithic is characterized by the use of knapped stone tools, although at the time humans also used  wood  and bone tools.