Indigo cultivation in India declined by the beginning of the 20th century because of

1. The question asks for the primary reason for the decline in Indigo cultivation in India by the beginning of the 20th century. 2. Option (A), peasant resistance to oppressive conduct, was a significant factor throughout the 19th century (e.g., the Indigo Revolt of 1859), but it wasn't the main cause for the sharp decline around the turn of the century. 3. Option (B) is the correct reason. The development and large-scale production of synthetic indigo dye in Germany (by BASF) in the late 1890s drastically reduced the demand for natural indigo. This made natural indigo cultivation largely unprofitable in the world market, leading to its rapid decline in India. 4. Option (C), national leaders' opposition, particularly highlighted by Gandhi's Champaran Satyagraha in 1917, addressed the exploitation associated with the cultivation, but the economic viability had already been severely undermined by synthetic dyes. 5. Option (D), Government control over the planters, was not the primary driver of the decline compared to the market disruption caused by new inventions.