What valuable resource does Sindbad find in large amounts on the island

And so, at his wife's suggestion, Sinbad sells all his possessions and returns with her to Baghdad, where at last he resolves to live quietly in the enjoyment of his wealth, and to seek no more adventures. ... On the return voyage the usual catastrophe strikes: Sinbad is captured and sold into slavery.

The answer should be d.

The image explain. how in the late 1900. sugar spread to the world