Answer:
Option C, To study ecology, we must separate living organisms from their environment
Explanation:
Environmental interaction between living organisms and the environment involves all the biological process such as nutrient cycle, ecosystems, food chains and food web, energy pyramids and relationship, response of an organism towards the changing environmental conditions, evolution, connection with all physical things etc.
In an ecosystem, the impact (both negative and positive) of both the living organism and environment is studied on each other by understanding their relationship for which presence of both of them is essential.
Hence, option C is correct