In human `_______________` is a small blind sac which hosts some symbiotic micro-organism.

Options

A. Caecum
B. Colon
C. Rumen
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a specific structure in the human body that is described as a "small blind sac" which hosts symbiotic microorganisms.

2. **Identifying Possible Answers**: The options provided are cecum, colon, rumen, and all of these. We need to determine which of these structures fits the description.

3. **Analyzing the Cecum**: The cecum is known to be a small pouch located at the junction of the small intestine and the large intestine. It is indeed a blind sac, meaning it has only one opening.

4. **Symbiotic Microorganisms in the Cecum**: The cecum hosts symbiotic microorganisms, primarily the bacterium E. coli. This bacterium plays a crucial role in the digestive process, particularly in the synthesis of certain vitamins like vitamin K and B complex.

5. **Evaluating Other Options**:
- **Colon**: The colon is part of the large intestine but is not a blind sac; it is a continuous tube.
- **Rumen**: The rumen is part of the digestive system in ruminant animals (like cows) and is not present in humans.

6. **Conclusion**: Based on the analysis, the correct answer to fill in the blank is "cecum". It is the small blind sac in humans that hosts symbiotic microorganisms.

**Final Answer**: In human **cecum** is a small blind sac which hosts some symbiotic microorganisms.

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