**Core Concept**
Movement is socio-economic level refers to the concept of social mobility, which is the ability of individuals or groups to change their social status or position within a society. This concept is closely related to the idea of social stratification, where individuals are categorized based on their economic, educational, and occupational characteristics.

**Why the Correct Answer is Right**
Social mobility can be influenced by various factors, including education, occupation, income, and family background. Individuals from lower socio-economic backgrounds may face barriers to social mobility due to limited access to education and job opportunities. In contrast, those from higher socio-economic backgrounds may have an advantage in terms of social connections, resources, and networks that facilitate upward mobility.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a clear direction or mechanism of social mobility.
**Option B:** This option is incorrect because it implies a one-way movement, whereas social mobility can occur in both upward and downward directions.
**Option C:** This option is incorrect because it does not accurately describe the concept of social mobility, which is a complex and multifaceted phenomenon.

**Clinical Pearl / High-Yield Fact**
The concept of social mobility is closely linked to health outcomes, with individuals from lower socio-economic backgrounds experiencing poorer health outcomes due to limited access to healthcare resources and social determinants of health.

**Correct Answer:** B.