**Core Concept**
Cholera is an infectious disease caused by Vibrio cholerae, a gram-negative bacterium. The pathogenesis of cholera involves the production of a toxin that affects the intestinal epithelium.

**Why the Correct Answer is Right**
The correct answer, B. Causes secretory diarrhoea, is due to the mechanism of action of the cholera toxin. The cholera toxin, also known as the cholera enterotoxin, is a potent ADP-ribosylating enzyme that activates the adenylate cyclase enzyme in the small intestine. This leads to an increase in intracellular cyclic AMP (cAMP) levels, causing a massive secretion of chloride and bicarbonate ions into the intestinal lumen. The resulting efflux of fluid and electrolytes into the intestine leads to the characteristic secretory diarrhea associated with cholera. The cholera toxin specifically targets the guanylate cyclase-C receptor, leading to an increase in guanosine-3',5'-cyclic monophosphate (cGMP) levels, which further contributes to the secretory diarrhea.

**Why Each Wrong Option is Incorrect**
**Option A:** The recent epidemic was actually due to the El Tor type of Vibrio cholerae, not the classical type.
**Option C:** Cholera is caused by an exotoxin, not an endotoxin. The cholera toxin is a potent exotoxin produced by Vibrio cholerae that causes the secretory diarrhea.
**Option D:** Vibriocidal antibodies do not correspond to susceptibility but rather to immunity. Individuals with high levels of vibriocidal antibodies are generally resistant to cholera infection.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the El Tor strain of Vibrio cholerae is more virulent than the classical strain and is responsible for the majority of recent cholera outbreaks.

**✓ Correct Answer: B. Causes secretory diarrhoea**