**Core Concept**
Non-pathogenic amoebae are free-living amoebae that do not cause disease in humans. These amoebae are commonly found in water, soil, and other environments and are harmless to humans. They play a crucial role in the ecosystem by serving as a food source for other organisms.

**Why the Correct Answer is Right**
The correct answer is C. Acanthamoeba. Acanthamoeba is a genus of amoebae that are non-pathogenic and free-living. They are commonly found in water, soil, and other environments and are known to feed on bacteria and other small organisms. Acanthamoeba is also known to form cysts, which are resistant to environmental stress and can survive for extended periods.

**Why Each Wrong Option is Incorrect**
* **Option A:** E. histolytica is a pathogenic amoeba that causes amoebiasis in humans. It is not non-pathogenic.
* **Option B:** E. coli is a type of bacteria, not an amoeba. It is a common cause of urinary tract infections and other bacterial infections.
* **Option D:** E. Hartmanni is a species of amoeba that is pathogenic to humans and causes amoebic meningoencephalitis.
* **Option E:** Balamuthia is a genus of amoebae that is pathogenic to humans and causes granulomatous amoebic encephalitis.

**Clinical Pearl / High-Yield Fact**
Acanthamoeba is commonly found in tap water, swimming pools, and soil, and can cause eye infections and other diseases in immunocompromised individuals.

**Correct Answer: C. Acanthamoeba**