The main excretory organs in man are

Options

A. Kidneys
B. Nephridia
C. Trachea
D. Lungs

Answer

**Step-by-Step Solution:**

1. **Understanding Excretion**: Excretion is the biological process through which waste products are removed from the body of an organism. It is essential for maintaining homeostasis and preventing the accumulation of toxic substances.

2. **Identifying the Options**: The question provides four options regarding the main excretory organs in humans:
- A) Kidney
- B) Nephridia
- C) Trachea
- D) Lungs

3. **Analyzing Each Option**:
- **Option A: Kidney**: The kidneys are bean-shaped organs located in the lower back. They play a crucial role in filtering waste products from the blood, regulating fluid balance, and producing urine through a process called ultrafiltration.
- **Option B: Nephridia**: Nephridia are excretory structures found in earthworms and some other invertebrates. They are not present in humans, making this option incorrect.
- **Option C: Trachea**: The trachea is a windpipe that carries air to and from the lungs. It is involved in respiration, not excretion, so this option is also incorrect.
- **Option D: Lungs**: While the lungs are vital for respiration, they are not considered excretory organs in the same sense as the kidneys. They help expel carbon dioxide, a waste product of respiration, but their primary function is gas exchange.

4. **Conclusion**: After analyzing all the options, it is clear that the main excretory organs in humans are the kidneys. Therefore, the correct answer is:
- **Answer**: A) Kidney

---