**Core Concept**
The recommended concentration of iodine in iodised salt at the consumer level is a public health measure to prevent iodine deficiency disorders, including goiter, cretinism, and cognitive impairment. Iodised salt is a key source of dietary iodine, particularly in areas where iodine-rich foods are scarce.

**Why the Correct Answer is Right**
The recommended concentration of iodine in iodised salt at the consumer level is 15-30 ppm (parts per million). This range allows for adequate iodine intake while minimizing the risk of iodine toxicity. The World Health Organization (WHO) recommends a concentration of 15 ppm, while some countries, like the United States, recommend 15-30 ppm. The iodine is typically added as potassium iodate or potassium iodide.

**Why Each Wrong Option is Incorrect**
**Option A:** While 45 ppm is higher than the recommended range, it's not the correct answer. Excessive iodine intake can lead to iodine toxicity, but 45 ppm is not the standard recommendation.
**Option B:** A concentration of 5 ppm is too low to effectively prevent iodine deficiency disorders. It may not provide adequate iodine for individuals with high requirements, such as pregnant women.
**Option C:** 0 ppm is not an option, as iodised salt is specifically designed to contain a measurable amount of iodine.

**Clinical Pearl / High-Yield Fact**
It's essential to note that iodised salt is not a substitute for other sources of iodine, such as seaweed, fish, and dairy products. A balanced diet that includes these foods can help ensure adequate iodine intake.

**Correct Answer:** C. 15-30 ppm