Final answer:
The statement regarding algae and protozoans contributing to biogenous sediment is A. true, as they are primary contributors through their calcareous or siliceous remains in aquatic environments.
Step-by-step explanation:
The organisms that contribute to biogenous sediment are chiefly algae and protozoans. This statement is A. true.
Biogenous sediments are derived from the remains of living organisms, and in aquatic environments, these primarily include algae, such as diatoms and dinoflagellates, and various protozoans.
Algae, particularly phytoplankton, and protozoans like foraminifera and radiolarians, play significant roles in sediment formation due to their calcareous or siliceous hard parts which, upon death, accumulate on the ocean floor.
Photosynthetic microorganisms such as algae are also important primary producers in aquatic ecosystems, contributing significantly to the world's photosynthesis, with organisms such as dinoflagellates, diatoms, and multicellular algae being particularly impactful.
Additionally, coral reefs are known to have symbiotic relationships with certain types of dinoflagellates, further illustrating the importance and contribution of these organisms to aquatic sediments and ecosystems.