It goes by the number of people who are eligible for and actually claiming unemployment benefits.
Yes, studying how mayfly population affects the number of trout in a stream is ecology.
Ecology seeks to unveil how different organism relate with one another as well as their environment.
Ecology is basically the study of distribution,abundance and relation of organisms and their interaction with their environment.
The awnser is b because needed money, goods, and land to build an empire and therefore had to tax