In a food web, producers are typically organisms that can create their own energy through processes like photosynthesis. In marine ecosystems, phytoplankton are considered the primary producers.
The organisms that get energy from producers (like phytoplankton) are typically herbivores or primary consumers. In your options, only zooplankton would be classified as consumers that feed on phytoplankton (the producers).
So the correct response is zooplankton.