Explanation:

- Birds, or aves, are warm-blooded animals.

- Warm-blooded animals maintain a constant body temperature.

- Aves have a heart that is specialized for efficient blood circulation.

- Option 1: Four-chambered heart

- Birds have a four-chambered heart.

- This includes two atria and two ventricles.

- This structure separates oxygenated and deoxygenated blood.

- Option 2: Two-chambered heart

- Found in fish.

- Consists of one atrium and one ventricle.

- Option 3: Five-chambered heart

- Not applicable to any known animal category.

- Option 4: Three-chambered heart

- Reptiles and amphibians typically have this.

- Includes two atria and one ventricle.