RBCs of mammals are

Options

A. Non-nucleated, biconcave and circular
B. Nucleated, biconvex, oval
C. Non-nucleated, biconvex, oval
D. Non-nucleated, biconvex, circular

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of RBCs**: Red blood cells (RBCs), also known as erythrocytes, are specialized cells in the blood responsible for transporting oxygen throughout the body.

2. **Nucleation**: In mammals, mature RBCs are non-nucleated. This means that once they reach maturity, they do not contain a nucleus. This adaptation allows for more space to carry hemoglobin, the protein that binds oxygen.

3. **Shape of RBCs**: The shape of mammalian RBCs is biconcave. This means that they are curved inwards on both sides, resembling a disc. This shape increases the surface area for gas exchange and allows them to deform as they pass through narrow capillaries.

4. **Other Characteristics**: The RBCs of mammals are circular in shape when viewed from above. They are also rich in hemoglobin, which gives blood its red color and is essential for oxygen transport.

5. **Conclusion**: Based on the characteristics discussed, the correct description of mammalian RBCs is that they are non-nucleated, biconcave, and circular.

### Final Answer:
**RBCs of mammals are non-nucleated, biconcave, and circular.**

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