The following statements regarding mammals are correct except

Options

A. Cloaca is present
B. External ear pinna present
C. Non-nucleated RBC
D. Excrete urea

Answer

To solve the question regarding the statements about mammals, we will analyze each statement provided and determine which one is incorrect.

### Step-by-Step Solution:

1. **Understanding Mammals**:
- Mammals belong to the class Mammalia and are characterized by certain features that distinguish them from other animal groups.

2. **Analyzing the Statements**:
- **Statement 1**: "Cloaca is present."
- In mammals, the excretory, reproductive, and digestive systems have separate openings. Therefore, mammals do not have a cloaca. This statement is incorrect.

- **Statement 2**: "External ear pinna is present."
- Mammals possess an external ear structure known as the pinna, which helps in sound amplification. This statement is correct.

- **Statement 3**: "Non-nucleated RBC."
- In mammals, the red blood cells (RBCs) lose their nucleus as they mature, allowing for more space to carry hemoglobin. This statement is correct.

- **Statement 4**: "They excrete urea."
- Mammals excrete nitrogenous waste primarily in the form of urea, which is less toxic than ammonia. This statement is correct.

3. **Conclusion**:
- The only incorrect statement regarding mammals is that "Cloaca is present." Therefore, the answer to the question is that this statement is the exception.

### Final Answer:
The following statements regarding mammals are correct except: **Cloaca is present.**