In which of the following, heart pump mixed blood

Options

A. Single circulation
B. Incomplete double circulation
C. Double circulation
D. both A and B

Explanation

To determine in which of the following the heart pumps mixed blood, we need to analyze the types of circulatory systems and heart structures.

### Step-by-Step Solution:

1. **Understand the Types of Circulation**:
- There are two main types of circulatory systems: single circulation and double circulation.
- Single circulation typically occurs in organisms with a two-chambered heart (one atrium and one ventricle), while double circulation occurs in organisms with a four-chambered heart (two atria and two ventricles).

2. **Identify the Heart Structure**:
- In a two-chambered heart (like in fish), blood flows in a single circuit: from the heart to the gills (where it gets oxygenated) and then to the rest of the body. This system does not mix oxygenated and deoxygenated blood.
- In a three-chambered heart (like in amphibians), there are two atria and one ventricle. Here, oxygenated and deoxygenated blood can mix in the ventricle, leading to mixed blood being pumped to the body.

3. **Analyze the Options**:
- If the options include a two-chambered heart (like in fish), it does not pump mixed blood.
- If the options include a three-chambered heart (like in amphibians), it does pump mixed blood because the single ventricle receives both oxygenated and deoxygenated blood.

4. **Conclusion**:
- The heart pumps mixed blood in organisms with a three-chambered heart (incomplete double circulation), where the ventricle mixes the blood before it is pumped out to the body.

### Final Answer:
The heart pumps mixed blood in organisms with a three-chambered heart (incomplete double circulation).

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