The correct answer is A. Ammonic compounds.
Chlamydomonas is a green algae that is found in both fresh and salt water. It is a unicellular organism that has a cell wall and a flagellum. Chlamydomonas is a photosynthetic organism, which means that it uses sunlight to produce its own food.
Ammonia is a nitrogenous compound that is found in many different forms in nature. It is a major component of urine and is also produced by the breakdown of organic matter. Ammonia is a very important nutrient for plants and algae. It is used in the synthesis of proteins, nucleic acids, and other essential compounds.
Chlamydomonas prefers water that is rich in ammonia. This is because ammonia is a very efficient source of nitrogen for the organism. Ammonia is also easily absorbed by the cells of Chlamydomonas.
The other options are incorrect because they are not as important for Chlamydomonas as ammonia. Uric acid, sulphur compounds, and urea are all nitrogenous compounds, but they are not as readily available to Chlamydomonas as ammonia. Additionally, these compounds are not as efficient as ammonia for the synthesis of proteins, nucleic acids, and other essential compounds.