The first option is: a map of Alexander the Great's route and the site of the sugar cane discovery.
This is because the central idea of the passage is to let the reader know about the context and events that led to Alexander the great know about the sweet reed. And for that reason a map of Alexander the Great's route would help understand the final result mentioned in the passage.
The second option is: a timeline showing when Darius l and Alexander the Great learned of sugar cane.
The passage shows that bacause of the books of Herodotus concerning emperor Darius I, greeks had a piece of knowledge of the sweet reed. And so, a timeline would help the reader visualize the relation between these two periods related to the discovery of sugar cane.