## Core Concept
Iodised oil, also known as Lipiodol, is a form of iodine supplementation used primarily in areas where iodine deficiency is prevalent. It provides a depot of iodine that is slowly released into the bloodstream, thereby prolonging its effect. The typical route of administration for such purposes is intramuscular (i/m).

## Why the Correct Answer is Right
The correct answer, which corresponds to a duration of **6-8 months** of protection against iodine deficiency disorders, is based on the pharmacokinetics of iodised oil. When administered intramuscularly, iodised oil acts as a reservoir for iodine, which is then gradually utilized by the body. This prolonged release allows for an extended period of protection against iodine deficiency, which can lead to conditions such as goiter, hypothyroidism, and cretinism if not addressed.

## Why Each Wrong Option is Incorrect
- **Option A:** This option suggests a much shorter duration of action (less than 6 months), which does not align with the known effects of iodised oil when given intramuscularly.
- **Option B:** Similarly, this option implies a shorter duration than what is typically observed with iodised oil administration.
- **Option D:** This option suggests a significantly longer duration of protection (more than 8 months), which, while possible in some cases, does not accurately represent the usual or expected duration of protection provided by a standard dose of 1 ml i/m.

## Clinical Pearl / High-Yield Fact
A key point to remember is that iodised oil is particularly useful in emergency situations or in areas with severe iodine deficiency where immediate correction is needed. The standard dose can vary but 1 ml i/m is commonly used for adults. It's also worth noting that iodised oil can interfere with thyroid function tests for a period after administration.

## Correct Answer: C.