Common nitrogenous wastes are

Options

A. Amino acid, uric acid and ammonia
B. Ammonia, urea and uric acid
C. Ammonia only
D. Guanine

Answer

### Step-by-Step Solution:

1. **Identify Common Nitrogenous Wastes**: The common nitrogenous wastes produced by organisms are ammonia, urea, and uric acid.

2. **Understand the Types of Nitrogenous Wastes**:
- **Ammonia**: This is the most toxic form of nitrogenous waste. It requires a large amount of water for its excretion, making it suitable for aquatic animals.
- **Urea**: Less toxic than ammonia, urea is excreted by mammals, marine fishes, and some amphibians. It requires less water compared to ammonia.
- **Uric Acid**: This is the least toxic form and is excreted by birds, reptiles, and terrestrial snails. It requires minimal water for excretion.

3. **Examples of Organisms Based on Nitrogenous Waste**:
- **Ammonia Excreters**: Bony fishes, aquatic amphibians, and aquatic insects primarily excrete ammonia.
- **Urea Excreters**: Mammals, marine fishes, and terrestrial amphibians (ureotelic organisms) excrete urea.
- **Uric Acid Excreters**: Birds, reptiles, and snails primarily excrete uric acid.

4. **Conclusion**: The most common nitrogenous wastes are ammonia, urea, and uric acid. Hence, the correct answer to the question is that these three are the common nitrogenous wastes.