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

Explanation

Because of its high value as a trading commodity, indigo was often referred to as blue gold. It has been the foundation of textile export from India for centuries. As its demand increased during the industrialization in Britain (as it was most suitable for cotton and also required for navy uniforms), its production also increased and so did the oppression by white planters. Although peasant resistance (Eg Indigo revolt) led to reduction in planters’ oppression. However, it was in reality its unprofitability in the world market because of new inventions that led to reduction in its production. Therefore, the correct answer is (b).