Correct Option (b)
Diatoms and Cyanobacteria are significant primary producers in marine food chains.
Diatoms are unicellular algae belonging to phytoplankton. They are photosynthetic organisms, utilizing sunlight to produce organic matter, thereby forming the base of many aquatic food webs and contributing substantially to global oxygen production.
Cyanobacteria, also known as blue-green algae, are photosynthetic prokaryotes. They contain chlorophyll-a and other pigments, enabling them to perform photosynthesis, synthesize their own food, and release oxygen. They are crucial primary producers in both marine and freshwater environments.
Incorrect Options
Copepods are small crustaceans that function as primary consumers (herbivores) in marine ecosystems. They feed on phytoplankton, including diatoms and cyanobacteria, and are not primary producers.
Foraminifera are heterotrophic protists. They obtain nutrients by consuming smaller organisms, such as phytoplankton and bacteria, making them consumers rather than producers in the food chain.
Therefore, options involving Copepods or Foraminifera as primary producers are incorrect.