An assemblage of populations of different species which interact through trophic and spatial relationship is...

Explanation

An ecosystem is a group of populations of different species that interact with one another through trophic (feeding) and spatial relationships. In simpler terms, it is a community of living organisms (plants, animals, and microbes) in a particular habitat, along with the nonliving components of that environment (such as air, water, and soil). Option A, City, is not the correct answer because it refers to a human settlement and does not involve interactions between different species. Option B, Community, is close but not quite right. While it refers to a group of populations of different species, it does not necessarily involve interactions through trophic and spatial relationships. Option C, Ecosystem, is the correct answer. It encompasses all the living organisms in a particular environment, as well as the nonliving components that shape that environment. Ecosystems can range from small, localized areas (such as a pond or a meadow) to large, global systems (such as the ocean or the atmosphere). Option D, Niche, refers to the specific role that a species plays within an ecosystem. While niches are important for understanding how different species interact with one another, they do not encompass the entire system of interactions that make up an ecosystem. In summary, the correct answer to this question is Option C, Ecosystem, because it best describes a group of populations of different species interacting through trophic and spatial relationships.