Which one of the following is the correct sequence of a food chain?

1. A food chain illustrates the flow of energy in an ecosystem, showing who eats whom. It starts with primary producers, followed by primary consumers, secondary consumers, and so on. 2. Diatoms are microscopic algae (phytoplankton). They perform photosynthesis and are primary producers, forming the base of many aquatic food chains. 3. Crustaceans (like copepods or krill, which are zooplankton) often feed on phytoplankton, including diatoms. Thus, they act as primary consumers. 4. Herrings are fish that feed on zooplankton, including small crustaceans. Therefore, they act as secondary consumers. 5. The correct sequence representing the flow of energy is Producer -> Primary Consumer -> Secondary Consumer. 6. Based on the roles identified, the correct sequence is Diatoms → Crustaceans → Herrings. This matches option (A).