Detailed Explanation:

Answer: Option 2 — its unprofitability in the world market because of new inventions

The decline of indigo cultivation in India by the early 20th century was primarily due to the invention of synthetic dyes in Germany (1880s), which were cheaper, easier to produce, and more consistent in quality than natural indigo. This led to a collapse in the global demand for natural indigo, making its cultivation economically unviable for planters in India. While peasant resistance (especially the Indigo Revolt of 1859-60) did occur earlier, the decisive factor for decline was the economic obsolescence caused by synthetic alternatives.

📝 Short Notes: Indigo Cultivation in India

• Colonial Indigo System: European planters forced Indian peasants to cultivate indigo on their land through tinkathia system (3/20th of land) and oppressive contracts.
• Indigo Revolt (1859-60): Peasant uprising in Bengal against exploitative planters, supported by missionaries and Bengali intellectuals; led to government inquiry (Indigo Commission, 1860).
• Champaran Satyagraha (1917): Gandhi's first major movement in India against indigo planters in Bihar, forcing abolition of the tinkathia system.
• Synthetic Dyes (1880s): German chemist Adolf von Baeyer synthesized indigo artificially; commercial production began in 1897 by BASF.
• Economic Impact: By 1913, synthetic indigo dominated the market; natural indigo cultivation became unprofitable and virtually disappeared by 1920s.