Why did Axum become important around 50 CE?

A. It had a trading port on the Red Sea that received goods from Egypt, Arabia, Greece, and Rome.

B. It became a center of Islamic learning and culture and had many schools, mosques, and Arab trade guilds.

C. It was converted to Christianity and became a hub for Christians traveling from Europe to the Middle East and Orient.

D. Its king conquered portions of the Middle East and north Africa, and the territories provided wealth in the form of tribute.