Concept:The term "ecosystem" was first proposed by the British ecologist Sir A.G. Tansley in 1935 to describe the interaction between living organisms and their physical environment.
Explanation:Tansley introduced the word "ecosystem" in his paper on vegetational concepts and terms. Before this, the term "biocoenosis" was used.
Eugene Odum was a famous ecologist who wrote the book "Fundamentals of Ecology" with his brother, but he did not coin the term.
Ernst Haeckel coined the word "ecology" (from Greek *Oikos* meaning house and *logos* meaning study) and proposed the theory of development, but not "ecosystem".
Hanns Reiter gave the concept of ecology in 1868, but again not the term ecosystem.
Thus, only Sir A.G. Tansley is credited with proposing the term ecosystem.
Answer:D. Tansely