Step 1: Understanding the concept of 'purity and pollution'.
Louis Dumont introduced the concept of 'purity and pollution' as a critical element in understanding the caste hierarchy in India. He viewed the caste system as based on a hierarchy of purity and pollution, with higher castes being considered more 'pure' than lower castes, who were seen as 'polluted'.
Step 2: Conclusion.
Louis Dumont's study emphasizes the ideological framework of purity and pollution in the structure of caste in India.
Final Answer: \[ \boxed{\text{The correct answer is (B) Louis Dumont.}} \]