**Core Concept**
The recommended minimum iodine level in iodized salt to prevent iodine deficiency disorders (IDD), such as cretinism and goiter, is established by global public health guidelines. This threshold ensures sufficient iodine intake to maintain normal thyroid function and fetal brain development.

**Why the Correct Answer is Right**
The World Health Organization (WHO) and the Global Iodine Program recommend a minimum iodine concentration of **15 ppm** (parts per million) in iodized salt to ensure effective prevention of iodine deficiency disorders. This level is sufficient to meet the daily iodine requirement of individuals across all age groups, especially pregnant and lactating women. Higher levels (like 30 ppm) may cause adverse effects, while lower levels (like 5 ppm) are insufficient to prevent IDD.

**Why Each Wrong Option is Incorrect**
Option A: 5 ppm is too low and fails to meet the minimum requirement for preventing IDD.
Option B: 30 ppm exceeds the recommended level and may lead to iodine toxicity or hyperiodemia.
Option D: 20 ppm is above the WHO-recommended minimum and not considered optimal for widespread use.

**Clinical Pearl / High-Yield Fact**
The **15 ppm** standard is a globally accepted benchmark—any iodized salt below this level is considered inadequate, and monitoring should be done to ensure compliance in public health programs.

✓ Correct Answer: C. 15 ppm