Which describes place? a. place is defined by it's unique characteristics. b. environment and people are interconnected. c. the world is divided into different regions based upon similarities and differences.

The best answer, here, would be (A).  Every "place" has particular characteristics that make it different from every other place on the planet. The concept of "place" deals with the physical and human characteristics of a particular "place." There are two particular ways of understanding the concept of "place":
Physical Place: Every "place" can be described in terms of its particular physical characteristics, including its weather, features, plants, and animals.
Human Place: Every "place" can be described in terms of its unique and particular human features such as its culture.