Concept:Nutrients move through living and non-living parts of an ecosystem in a repeated pathway.
Explanation:The continuous movement and recycling of nutrients is called a nutrient cycle or biogeochemical cycle.
It involves processes that replenish elements like carbon, nitrogen, and water.
In the given options, the correct term for this pathway is simply a "cycle".
Pyramids of energy and numbers show feeding relationships, not nutrient circulation.
A food chain shows the flow of energy, not the replenishment of nutrients.
Answer:A. cycle