The correct answer is D. Oxalic acid.
An organic acid is an acid that contains carbon. Organic acids are found in many different plants and animals, and they play an important role in many biological processes. Some common organic acids include acetic acid (vinegar), citric acid (found in citrus fruits), and lactic acid (produced by muscles during exercise).
Carbonic acid is a weak acid that is found in rainwater and in the air. It is formed when carbon dioxide dissolves in water. Sulphuric acid is a strong acid that is used in many industrial processes. Nitric acid is a strong acid that is used in many manufacturing processes.
Oxalic acid is a weak acid that is found in many plants, including rhubarb and spinach. It is also used in some cleaning products.