Specially in hilly areas people suffering from retarted growth and mental disability, it is caused mainly by the deficiency of

Options

A. protein
B. phosphorus
C. iodine
D. calcium

Explanation

To solve the question regarding the deficiency causing retarded growth and mental disability in people living in hilly areas, we can follow these steps:

### Step 1: Understand the Context
- The question specifies that the issue is prevalent in hilly areas. It suggests that environmental factors, particularly related to soil and food, may be involved.

### Step 2: Identify Nutritional Deficiencies
- In hilly regions, the soil is often poor in certain nutrients. We need to consider which nutrient deficiencies are common in these areas and how they relate to growth and mental development.

### Step 3: Focus on Iodine Deficiency
- It is known that iodine deficiency can lead to serious health issues, including goiter, retarded growth, and mental disabilities. This is particularly relevant in areas where the soil lacks iodine, which affects the food grown there.

### Step 4: Conclude the Answer
- Based on the information gathered, the deficiency that mainly causes retarded growth and mental disability in hilly areas is iodine deficiency. Therefore, the correct answer is option C: iodine.

### Final Answer
- The deficiency mainly causing retarded growth and mental disability in hilly areas is iodine deficiency.

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