Elimination of which substance requires large amount of water ?

Options

A. Urea
B. Creatinine
C. Ammonia
D. Uric acid

Answer

To solve the question of which substance requires a large amount of water for elimination, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Substances**: We have four substances to consider: urea, creatinine, ammonia, and uric acid. Each of these has different properties and levels of toxicity.

2. **Analyzing Ammonia**: Ammonia (NH3) is a highly toxic nitrogenous waste product. Due to its toxicity, it must be eliminated quickly from the body.

3. **Solubility in Water**: Ammonia is highly soluble in water. This means that to safely eliminate ammonia, organisms need to dilute it with a significant amount of water to avoid toxicity.

4. **Excretion Mechanism**: Organisms that excrete ammonia are known as ammonotelic organisms. This includes certain fish, crustaceans, and amphibian larvae (like tadpoles).

5. **Comparison with Other Substances**:
- **Urea**: Less toxic than ammonia and requires less water for excretion.
- **Creatinine**: A waste product from muscle metabolism, also requires less water for elimination.
- **Uric Acid**: The least toxic and is excreted as a paste, requiring minimal water.

6. **Conclusion**: Among the options provided, ammonia requires the largest amount of water for its elimination due to its high toxicity and solubility.

### Final Answer:
The substance that requires a large amount of water for elimination is **ammonia**.

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