A series showing energy flow between organisms

• A. Food web
• B. Energy pyramid
• C. Producer
• D. Food chain

Answer: (D)

The idea being tested is how energy moves through an ecosystem in a simple, linear sequence. A single line of organisms showing who eats whom illustrates energy flow directly from one member to the next, starting with a producer and passing to herbivores and then to predators. That straightforward path is what a food chain represents. The other options describe broader or different concepts: a food web shows many interconnected feeding relationships, an energy pyramid depicts the amount of energy at each trophic level rather than a specific sequence, and a producer is simply the starting organism, not a representation of the energy transfer itself.