The correct option is A Primary sector
The primary sector contributed the largest share to India's GDP post-independence. Accordingly, agiculture contributed 51.81% (1950–51), 42.56% (1960–61), and 41.95% (1970–71). The reason can be attributed to the requirement of food post-independence since the British colonial government failed to ensure food security for the population of India during their rule. However, the contribution of agriculture has come down to less than 20% in the recent years with the service sector being the major contributor to India's gross domestic product (GDP).