The foul smell of urine is mainly due to the bacterial decomposition of certain components in the urine. In this case, we are looking at the foul smell of urine from a healthy man who has been having a healthy diet.

Option 1 suggests that the foul smell is due to the decomposition of urea into sulfur dioxide. However, this is not accurate as sulfur dioxide does not typically contribute to the foul smell of urine.

Option 2 suggests that the foul smell is due to the decomposition of sugar into carbon dioxide. While sugars can be present in urine, they are not typically responsible for the foul smell. Additionally, carbon dioxide is an odorless gas.

Option 3 suggests that the foul smell is due to the decomposition of lipids into methane. However, lipids are not a significant component of urine and are unlikely to contribute to the foul smell.

Option 4, which is the correct answer, suggests that the foul smell is due to the bacterial decomposition of urea into ammonia. Urea is a waste product produced by the body and is excreted in urine. When urea is broken down by bacteria, it can produce ammonia, which has a strong and unpleasant odor.

In summary, the foul smell of urine is mainly due to the bacterial decomposition of ure