Of the following true about bilirubin and biliviridin.

Options

A. They help in emulsification of fats
B. Plays important role in formation of micelles
C. Formed due to breakdown of RBCs
D. They act as enzymes

Answer

### Step-by-Step Solution:

1. **Understanding Bilirubin and Biliverdin**:
- Bilirubin and biliverdin are pigments that are produced from the breakdown of hemoglobin in red blood cells (RBCs). When RBCs are destroyed, hemoglobin is released and subsequently broken down into these two substances.

2. **Analyzing the Options**:
- We need to evaluate the given options to determine which statement is true regarding bilirubin and biliverdin.

3. **Evaluating Option 1**:
- **Statement**: They help in the emulsification of fat.
- **Analysis**: This statement is incorrect. Emulsification of fat is primarily done by bile salts, not by bilirubin or biliverdin.

4. **Evaluating Option 2**:
- **Statement**: They play an important role in the formation of micelles.
- **Analysis**: This statement is also incorrect. Micelles are formed by bile salts and not by bilirubin or biliverdin.

5. **Evaluating Option 3**:
- **Statement**: They are formed due to the breakdown of RBCs.
- **Analysis**: This statement is correct. Bilirubin and biliverdin are indeed formed as a result of the breakdown of red blood cells.

6. **Evaluating Option 4**:
- **Statement**: They act as enzymes.
- **Analysis**: This statement is incorrect. Bilirubin and biliverdin are not enzymes; they are pigments and do not catalyze any biochemical reactions.

7. **Conclusion**:
- The only true statement among the options provided is option number three: "formed due to breakdown of RBCs."

### Final Answer:
- The correct answer is: **Option 3: formed due to breakdown of RBCs.**