## Core Concept
Gastric lavage, also known as stomach pumping, is a procedure where the stomach is flushed of its contents. It's used in certain cases of poisoning but is contraindicated in specific scenarios due to the risk of causing more harm than benefit. The question tests the understanding of when gastric lavage is contraindicated in different types of poisoning.

## Why the Correct Answer is Right
In cases of **corrosive poisoning** (option 3), gastric lavage is generally contraindicated. This is because corrosive substances cause severe burns to the mucosal lining of the esophagus and stomach. Performing gastric lavage could exacerbate these injuries, potentially leading to perforation of the esophagus or stomach.

## Why Each Wrong Option is Incorrect
- **Option A: Kerosene poisoning** - Gastric lavage might be considered in some cases of kerosene poisoning but is not the best answer here as it's not absolutely contraindicated; however, it's risky due to the potential for aspiration.
- **Option B: Organo-phosphorus poisoning** - Gastric lavage might be performed in certain cases of organophosphate poisoning if the patient presents early, though it's not the ideal treatment.
- **Option D: Iron poisoning** - While supportive care and sometimes deferoxamine are treatments for iron poisoning, gastric lavage might be considered in severe cases if the patient presents very early.

## Clinical Pearl / High-Yield Fact
A key point to remember is that in **corrosive poisoning**, the primary concern is the risk of esophageal or gastric perforation. Thus, endoscopy is often recommended before any consideration of lavage to assess the extent of damage.

## Correct Answer: C. Corrosive poisoning