Answer:
D. large-sized fishes
Explanation:
The energy flow in the trophic level from highest to lower level is as follows:
Large-Sized Fishes => Fishes and Crabs (Larvae) => Zooplankton => Diatoms/Algae.
The concentration of toxics or chemical substance increases from lower level (primary producers) to highest level, so the organism at apex contain highest concentration of chemical fertilizer.
In this example, large-sized fishes have highest concentration of chemical fertilizer.
Hence, the correct answer is D. large-sized fishes.
