**Core Concept**
Epidemic dropsy is a condition characterized by the accumulation of fluid in the subcutaneous tissue, leading to swelling of the limbs, particularly in the upper body. This condition is caused by the consumption of mustard oil contaminated with a toxic compound, which triggers a series of pathophysiological events.

**Why the Correct Answer is Right**
The consumption of contaminated mustard oil leads to the accumulation of toxic compounds in the body, which triggers the release of histamine and other vasoactive mediators. These mediators cause the dilation of blood vessels, leading to increased permeability and fluid leakage into the interstitial space. As a result, the subcutaneous tissue becomes edematous, causing the characteristic swelling of the limbs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because epidemic dropsy is not caused by a deficiency in vitamin C, which is associated with scurvy.
* **Option B:** This option is incorrect because chronic arsenic poisoning causes skin lesions, hyperpigmentation, and gangrene, but not epidemic dropsy.
* **Option C:** This option is incorrect because anthrax is a bacterial infection caused by Bacillus anthracis, which presents with fever, skin lesions, and respiratory symptoms, but not epidemic dropsy.

**Clinical Pearl / High-Yield Fact**
Epidemic dropsy is a classic example of a condition caused by food contamination, highlighting the importance of proper food handling and storage practices to prevent outbreaks.

**Correct Answer: D. Mineral oil**