**Core Concept**
The diagnosis of skin infections, particularly those caused by zoonotic pathogens, requires a combination of clinical acumen and laboratory techniques. In this scenario, the patient's occupation and the progression of the lesion suggest a possible cutaneous anthrax infection.

**Why the Correct Answer is Right**
Cutaneous anthrax is caused by Bacillus anthracis, a gram-positive, rod-shaped bacterium. The best stain to identify B. anthracis is the **Wright's stain**, which highlights the characteristic "boxcar" or "square" arrangement of the exosporium around the spores. This distinctive staining pattern is a key diagnostic feature of B. anthracis.

**Why Each Wrong Option is Incorrect**
**Option A:** Gram stain is not the best choice for identifying B. anthracis, as it may not reveal the characteristic spore morphology.

**Option B:** Acid-fast stain is typically used for identifying mycobacteria, such as M. tuberculosis, and is not useful for diagnosing B. anthracis.

**Option C:** Neisser stain is primarily used for identifying Neisseria species, such as N. gonorrhoeae, and is not applicable in this scenario.

**Clinical Pearl / High-Yield Fact**
When suspecting cutaneous anthrax, it is essential to consider the patient's occupation and exposure history, as well as the clinical presentation, which often includes a painless, black eschar at the site of the lesion.

**Correct Answer:** C. Neisser stain.