Ureotelic organisms like mammals excrete urea in their urine, that is formed in:

Options

A. spleen
B. kidney
C. liver
D. gall bladder

Explanation

**Step-by-Step Solution:**

1. **Understanding Ureotelic Organisms**: Ureotelic organisms, such as mammals, primarily excrete urea as their main nitrogenous waste product. This distinguishes them from other types of organisms that may excrete ammonia or uric acid.

2. **Identifying the Excretory Product**: In mammals, urea is the primary excretory product found in urine. This means that the formation of urea is a critical process in the metabolism of nitrogenous compounds.

3. **Determining the Site of Urea Formation**: The question asks where urea is formed in the body. The options provided are:
- A) Spleen
- B) Kidney
- C) Liver
- D) Gallbladder

4. **Analyzing Each Option**:
- **Spleen**: The spleen is involved in filtering blood and recycling iron from red blood cells, but it does not play a role in the formation of urea.
- **Kidney**: The kidneys are crucial for excretion and filtering waste from the blood, but they do not synthesize urea. Instead, they filter urea from the blood to be excreted in urine.
- **Liver**: The liver is the primary site for the metabolism of amino acids, where ammonia is converted into urea through the urea cycle. This is the key process for urea formation.
- **Gallbladder**: The gallbladder stores bile produced by the liver, but it does not participate in the formation of urea.

5. **Conclusion**: Based on the analysis, the correct answer is C) Liver, as it is the organ responsible for the formation of urea in ureotelic organisms like mammals.

---