Concept:The phrase 'Unity in Diversity' refers to the idea that a nation can thrive by combining different cultures, languages, and traditions. It was popularized by a key Indian leader.Explanation:The phrase 'Unity in Diversity' was coined and popularized by Pt. Jawaharlal Nehru, the first Prime Minister of India. He used it to describe India's strength, which comes from its vast diversity of cultures and communities. Other leaders are associated with different slogans or roles. Subhash Chandra Bose is known for "Give me blood, and I shall give you freedom." Sardar Vallabh Bhai Patel worked to unify princely states but did not coin this phrase. Mahatma Gandhi promoted communal harmony but did not use this specific phrase. Therefore, among the given options, only Pt. Jawaharlal Nehru is credited with coining 'Unity in Diversity'.Answer:C. Pt. Jawaharlal Nehru