**Core Concept**
The question tests the student's knowledge of bacterial characteristics, specifically spore formation. Bacterial spores are highly resistant, dormant structures formed by some bacteria for survival.

**Why the Correct Answer is Right**
Since the correct answer is not explicitly stated, let's analyze the common spore-forming bacteria. *Bacillus* and *Clostridium* are well-known spore-formers.

**Why Each Wrong Option is Incorrect**
**Option A:** If this were a spore-forming bacterium like *Bacillus*, it would be incorrect because the question seeks a non-spore former.
**Option B:** Similarly, if this option represented a spore-forming genus like *Clostridium*, it would be an incorrect choice for the same reason.

**Clinical Pearl / High-Yield Fact**
Remember that *Bacillus* and *Clostridium* species are notorious for their spore-forming capabilities, which make them highly resistant to environmental stresses and certain antimicrobial therapies.

**Correct Answer:** Correct Answer: D. *Neisseria*.