Detailed Explanation:

The triangular trade between Britain, India, and China (18th–19th century) relied on opium as its economic cornerstone.

Britain cultivated opium in Bengal and Bihar, exported it to China (where it was sold illegally), and used the profits to purchase Chinese tea and silk without draining British silver reserves. This system bypassed Britain's trade deficit with China and funded colonial expansion, ultimately leading to the Opium Wars (1839–1842, 1856–1860).