Which one resides in the mouth of human beings

Options

A. Entamoeba coli
B. Entamoeba histolytica
C. Entamoeba gingivalis
D. Amoeba proteus.

Answer

To determine which organism resides in the mouth of human beings, we will analyze the given options one by one.

### Step 1: Identify the Options
The options provided are:
1. Entamoeba coli
2. Entamoeba histolytica
3. Entamoeba gingivalis
4. Amoeba proteus

### Step 2: Analyze Each Option
- **Entamoeba coli**: This organism is known to inhabit the gastrointestinal tract and is associated with acute amoebiasis. It does not reside in the mouth.

- **Entamoeba histolytica**: This species is responsible for amoebiasis or amoebic dysentery, and it also inhabits the gastrointestinal tract. Therefore, it is not found in the mouth.

- **Entamoeba gingivalis**: This protozoan is specifically associated with the oral cavity and is known to cause gum disease (pyorrhea). This indicates that it resides in the mouth.

- **Amoeba proteus**: This species is a non-parasitic amoeba found in freshwater environments and does not inhabit the human mouth.

### Step 3: Conclusion
Based on the analysis, the organism that resides in the mouth of human beings is **Entamoeba gingivalis**.

### Final Answer
**Entamoeba gingivalis**

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