**Core Concept**
Malignant pustules are a characteristic skin lesion associated with a specific bacterial infection. They are a type of cutaneous manifestation resulting from the toxin-mediated effects of the causative organism.

**Why the Correct Answer is Right**
Malignant pustules are a hallmark of cutaneous anthrax, caused by the bacterium *Bacillus anthracis*. The toxin produced by this bacterium, specifically the anthrax toxin, leads to the formation of these pustules. The toxin's edema factor causes a rapid increase in capillary permeability, resulting in the characteristic skin lesion. The lesion progresses through several stages, including a painless, pruritic papule that eventually transforms into a pustule, and eventually, a black eschar.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not relate to the specific type of skin lesion caused by *Bacillus anthracis*.
**Option B:** This option is incorrect as it does not accurately describe the characteristic skin lesion associated with cutaneous anthrax.
**Option C:** This option is incorrect as it does not correctly identify the causative organism of malignant pustules.

**Clinical Pearl / High-Yield Fact**
Malignant pustules are a clinical manifestation of cutaneous anthrax, which can be distinguished from other skin lesions by its characteristic progression and association with a specific bacterium. A high index of suspicion is necessary for early diagnosis and treatment.

**Correct Answer: C. Bacillus anthracis.**