Choose the correct statements
A) Uric acid is converted into allantoin by the action of uricase enzyme, in humans
B) Most of the ammonia is lost as ammonium ions across the epithelium of gills, in bony fishes
C) Trimethylamine oxide protects body proteins from the damaging effect of uric acid in cartilaginous fishes

Options

A. A, B only
B. B, C only
C. A, C only
D. All

Answer

To solve the question, we need to evaluate each of the statements provided and determine which ones are correct.

### Step-by-Step Solution:

1. **Evaluate Statement A**:
- **Statement**: "Uric acid is converted into allantoin by the action of uricase enzyme, in humans."
- **Analysis**: Uric acid can indeed be converted into allantoin by the enzyme uricase. However, humans lack the uricase enzyme, meaning this conversion does not occur in humans.
- **Conclusion**: This statement is **false**.

2. **Evaluate Statement B**:
- **Statement**: "Most of the ammonia is lost as ammonium ions across the epithelium of gills, in bony fishes."
- **Analysis**: Bony fishes excrete ammonia primarily through their gills in the form of ammonium ions (NH4+). This process is known as ammonotelism, and it is a common method of excretion for many aquatic organisms.
- **Conclusion**: This statement is **true**.

3. **Evaluate Statement C**:
- **Statement**: "Trimethylamine oxide protects body proteins from the damaging effect of uric acid in cartilaginous fishes."
- **Analysis**: Trimethylamine oxide (TMAO) is indeed present in cartilaginous fishes (like sharks and rays) and serves to stabilize proteins against the damaging effects of urea and possibly uric acid. This protective role is well-documented in these species.
- **Conclusion**: This statement is **true**.

### Final Evaluation:
- **Correct Statements**:
- Statement A: **False**
- Statement B: **True**
- Statement C: **True**

Thus, the correct options are **B and C**.