Which of the following is an "acquired" trait to classify tribes in India?

The correct option is livelihood.

In sociological and anthropological studies, the traits used to classify tribal communities in India are broadly categorized into two types: permanent traits and acquired traits.

Permanent Traits:
These are biological, geographical, or ecological characteristics that are inherent, natural, and remain relatively stable over time. Examples include:
1. Language: The linguistic family to which a tribe belongs (such as Indo-Aryan, Dravidian, Austric, or Tibeto-Burman) is a permanent cultural-historical classification.
2. Racial features: Physical anthropological characteristics (such as Mongoloid, Proto-Australoid, Negrito, etc.) are biological and inherited.
3. Habitat: The ecological or geographical region where a tribe originally resides (such as hills, forests, plains, etc.) is a fixed environmental feature.

Acquired Traits:
These are socio-economic, cultural, and political attributes that are adopted, learned, or changed over time through interaction with the wider society and economic environment. Examples include:
1. Livelihood: The mode of economy and sustenance (such as food gathering, shifting cultivation, settled agriculture, pastoralism, or industrial labor) is a choice or adaptation influenced by historical and external factors, making it an acquired classification trait.
2. Extent of Assimilation: The degree of integration into Hindu society or other mainstream religions is also an acquired sociological trait.

Therefore, among the given choices, livelihood is classified as an "acquired" trait, whereas language, racial features, and habitat are classified as permanent traits.