The correct answer is - Exports grew significantly in the 1820's.
This graph shows us the exports of opium by the British toward China. Starting from the year of 1729 the exports of opium in China constantly grew, though relatively slowly. In 1790 there's significant rise in the exports, but that it kind of stagnates and the growth is minimal in next three decades.
From the begging of the 1820's to the end of the 1820's the exports of opium start to grow very quickly. The rise in exports was so quick that in just this decade the exports of opium went up by around three times (tripled).
That trend of rapid growth in the opium exports continued in the next decade, the 1830's, as well.