The study of ecology focuses specifically on:

A. the world that is all around us.
B. the world of living things in our planet.
C. the mutual relationship between organisms and the natural world.
D. anything having to do with life.

I chose c

A.. the world that is all around us.

http://www.merriam-webster.com/dictionary/ecology

The study of ecology focuses specifically on the mutual relationship between organisms and the natural world. To determine the correct answer, we can look at the definitions of ecology and the options provided.

Ecology is the branch of biology that deals with the relations of organisms to one another and to their physical surroundings. It involves understanding how organisms interact with each other and with the environment they live in.

Looking at the options:

A. "The world that is all around us" is a bit vague and doesn't specifically refer to the mutual relationship between organisms and the natural world.

B. "The world of living things on our planet" is closer to the correct answer, but it doesn't explicitly mention the mutual relationship between organisms and the natural world.

C. "The mutual relationship between organisms and the natural world" accurately describes the focus of ecology, making it the correct answer.

D. "Anything having to do with life" is too broad and doesn't narrow down the specific focus of ecology.

So, the correct answer is C. the mutual relationship between organisms and the natural world.