Which of the following is not an excretory organ?

Options

A. Spleen
B. Kidney
C. Liver
D. Lungs

Explanation

To determine which of the following is not an excretory organ, we need to analyze each option provided: spleen, kidney, liver, and lungs.

### Step-by-Step Solution:

1. **Understanding Excretory Organs**: Excretory organs are responsible for the removal of waste products from the body. This includes not only urine and feces but also gases like carbon dioxide and other metabolic waste.

2. **Analyzing Each Option**:
- **Lungs**: The lungs are involved in the excretion of carbon dioxide (CO2) from the body. They play a dual role as both respiratory and excretory organs.
- **Liver**: The liver is crucial in the metabolism of proteins and the conversion of ammonia into urea, which is then excreted. Thus, it also functions as an excretory organ.
- **Kidney**: The kidneys are primary excretory organs, responsible for filtering blood and removing waste products through urine formation. They are essential for excretion.
- **Spleen**: The spleen is primarily involved in the filtration of blood and the recycling of iron from red blood cells. It does not play a direct role in the excretion of metabolic waste products.

3. **Conclusion**: Based on the analysis, the spleen does not function as an excretory organ. Therefore, the correct answer is **spleen**.

### Final Answer:
The organ that is not an excretory organ is **spleen**.

---