A four-chambered heart is characteristic of :
(a) bony fish
(b) mammals
(c) amphibians
(d) none of these

Options

A. bony fish
B. mammals
C. amphibians
D. none of these

Explanation

To determine which group of animals has a four-chambered heart, we can analyze the options provided:

1. **Understanding the Heart Structure**:
- The heart can have different structures based on the type of animal. It can be two-chambered, three-chambered, or four-chambered.

2. **Analyzing Each Option**:
- **(a) Bony Fish**: Bony fish typically have a two-chambered heart, consisting of one atrium and one ventricle. This structure is not capable of separating oxygenated and deoxygenated blood effectively.
- **(b) Mammals**: Mammals possess a four-chambered heart, which includes two atria and two ventricles. This structure allows for the complete separation of oxygenated and deoxygenated blood, which is crucial for efficient metabolism and energy production.
- **(c) Amphibians**: Amphibians generally have a three-chambered heart, consisting of two atria and one ventricle. This configuration does not fully separate oxygenated and deoxygenated blood.
- **(d) None of these**: This option suggests that none of the listed groups have a four-chambered heart, which is incorrect since mammals do.

3. **Conclusion**:
- Based on the analysis, the only group that possesses a four-chambered heart is **mammals**. Therefore, the correct answer is **(b) mammals**.

**Final Answer**: (b) mammals

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