**Core Concept**
Anthropometric measures are used to assess malnutrition in individuals. Age-independent measures are essential to accurately evaluate nutritional status across different age groups. The body mass index (BMI) is a widely used anthropometric measure that does not account for age.

**Why the Correct Answer is Right**
The correct answer, **BMI**, is an age-independent measure because it calculates body mass in relation to height (kg/m^2). BMI is a reliable indicator of underweight, normal weight, overweight, and obesity. It is calculated using the formula: BMI = weight (in kg) / height (in meters) squared.

**Why Each Wrong Option is Incorrect**
**Option A:** Mid-upper arm circumference (MUAC) is an age-dependent measure, as it is used primarily in children under 5 years of age.
**Option B:** Weight-for-age is an age-dependent measure, as it does not account for height differences across various age groups.
**Option C:** Skin fold thickness is an age-dependent measure, as it requires specific reference values for different age groups.

**Clinical Pearl / High-Yield Fact**
BMI is a useful screening tool for malnutrition, but it has limitations. For example, athletes or individuals with muscle wasting may have a high BMI despite being malnourished. Always consider BMI in conjunction with other anthropometric measures and clinical assessment.

**Correct Answer: C. Mid-upper arm circumference (MUAC) is an age-dependent measure, as it is used primarily in children under 5 years of age.**