To solve this problem, we need to identify which organism excretes nitrogenous waste in the form of pellets or paste. Let's analyze each option:$\newline \bullet$Option 1: Ornithorhynchus (Platypus) - This is a monotreme mammal that excretes urea in liquid form, not as pellets or paste.$\newline \bullet$Option 2: Salamandra (Salamander) - This is an amphibian that typically excretes urea in liquid form.$\newline \bullet$Option 3: Hippocampus (Seahorse) - This is a marine fish that excretes ammonia, which is dissolved in water, not as pellets or paste.$\newline \bullet$Option 4: Pavo (Peacock) - This is a bird, and birds excrete uric acid in the form of a semi-solid paste or pellets.$\newline$Birds, including peacocks, excrete nitrogenous waste primarily as uric acid, which is less toxic and conserves water by being excreted as a paste or pellets.$\newline$Therefore, the correct answer is Option 4: Pavo.