Which phrase best describes an ecosystem?

a. all living things and the places on earth where they are found
b. organisms interacting with each other and with nonliving things in a certain region
c. the variety of organisms on earth or in a particular area of the biosphere
d. a group of living things that can interbreed to reproduce

Atherapist at a free university clinic treats elementary school children with behavior problems who are referred by a social service agency. she is also a doctoral candidate who proposes using data she has and will collect about the children for a case-based research project. describe the type of parental permission which is required in this case?