The correct answer is "1 and 3 only" because both the excretion of urea by animals and the death of vegetation contribute nitrogen to the soil effectively. Urea is a nitrogenous waste that, when decomposed by soil bacteria, is converted into forms that plants can utilize. Similarly, the decomposition of dead vegetation releases nitrogen compounds back into the soil. In contrast, burning coal primarily releases carbon dioxide and other pollutants and does not contribute nitrogen. This understanding aligns with concepts from ecological and agricultural studies on nutrient cycling and soil health, which are integral in UPSC syllabus preparations.