A parasite named remains in the large intestine of the infected person and is responsible for blood stool sometimes.

Options

A. Entamoeba histolytica
B. Trypanosoma brucei
C. Ascaris lumbricoides
D. HBV

Answer

**Step-by-Step Solution:**

1. **Identify the Parasite**: The question asks for a parasite that resides in the large intestine and can cause blood in the stool.

2. **Consider the Options**: The options provided include:
- Amoeba (specifically, Entamoeba histolytica)
- Trypanosoma brucei
- Ascaris lumbricoides
- Hepatitis B Virus (HBV)

3. **Analyze Each Option**:
- **Amoeba (Entamoeba histolytica)**: This is a protozoan parasite that infects the large intestine and causes amoebiasis, also known as amoebic dysentery. Symptoms include abdominal pain, cramps, and blood-stained stools.
- **Trypanosoma brucei**: This parasite causes sleeping sickness and is transmitted by the tsetse fly. It does not reside in the large intestine.
- **Ascaris lumbricoides**: This is a roundworm that causes ascariasis, primarily affecting the intestines but does not specifically cause blood in the stool.
- **Hepatitis B Virus (HBV)**: This virus primarily affects the liver and does not cause symptoms related to the large intestine.

4. **Conclusion**: Based on the analysis, the correct answer is **Entamoeba histolytica**, as it is the only parasite listed that resides in the large intestine and can lead to blood in the stool.

**Final Answer**: The parasite that remains in the large intestine of the infected person and is responsible for blood stool sometimes is **Entamoeba histolytica**.

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