China grew very wealthy mainly as a result of discovering gold.
Chinese trading.
skilled Chinese artisans.
agriculture.

China is the world's largest manufacturing economy and exporter of goods.

it is the largest trading nation in the world and plays a prominent role in international trade.

answer is B:Chinese trading.

if I'm wrong, sorry

islam spread slowly through much of africa through trade and preaching.

i would say it is the roman empire europe after the norman conquest.