Who among the following proposed the term ‘ecosystem’?

Correct option is A

An ecosystem is the basic ecological unit in which living organisms interact among themselves and with their surrounding physical environment.
 The term ecosystem was proposed by Sir A.G. Tansley in the year 1935.
 A.G. Tansley first used the word ecosystem in his well-known paper on vegetational concepts and terms.
 The word 'biocoenosis' was used before that.