Question

cod feed on _.
algae
zooplankton
grass
seals

Explanation:

Cod are carnivorous fish that typically feed on smaller aquatic organisms. Zooplankton are small - floating animals that are a common food source for many fish species including cod. Algae are primary producers and not a main food for cod. Grass is a terrestrial plant and not relevant to cod's diet. Seals are much larger than cod and are predators of cod rather than food for cod.

Answer:

B. zooplankton