The correct answer is:

1 and 3 only.

Both the excretion of urea by animals and the death of vegetation can add nitrogen to the soil.

1. Excretion of urea by animals: Animals excrete urea as a waste product, and urea contains nitrogen. When animals urinate or defecate, the nitrogen from urea enters the soil as organic nitrogen, which can be converted into forms that plants can use.

3. Death of vegetation: When plants die and decompose, the organic matter breaks down, releasing nitrogen into the soil. This process is known as mineralization, and it contributes to the nitrogen content in the soil.

2. Burning of coal by man: Burning coal does not directly add nitrogen to the soil. The burning of coal primarily releases carbon dioxide, sulfur dioxide, and other pollutants into the atmosphere, but not nitrogen.

Therefore, the correct answer is "1 and 3 only."