The least toxic excretory product is:

Explanation

Option C is correct.The correct answer is uric acid, which is the least toxic excretory product. It is excreted in a solid or semi-solid form and conserves water, making it ideal for animals like birds and reptiles living in arid environments. Ammonia, on the other hand, is highly toxic and requires a significant amount of water to be safely excreted, which is why it is typically excreted by aquatic animals. Urea is less toxic than ammonia and is excreted by mammals and amphibians, requiring moderate amounts of water. Fatty acids are not directly involved in nitrogenous waste excretion.