AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Answer: C – Opium
Opium shipments to China grew rapidly from the 1820s and became, for a while, India's single largest export. Britain grew opium in India, exported it to China, and used the earnings to finance its tea imports from China.
Source: Chapter 3, Section 2.6 – Indian Trade, Colonialism and the Global System
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The passage explicitly states: "opium shipments to China grew rapidly from the 1820s to become for a while India's single largest export." The key detail examiners look for is the link between opium → China → financing Britain's tea trade. Don't confuse this with raw cotton (which rose sharply as an export but was not described as the single largest) or indigo (important but secondary).