Read each question carefully. Determine the best answer to the question from the four answer choices provided. The birth of the Prophet Muhammad in A. D. 570 forever shaped Saudi Arabia. Today, many Arabs refer to the era before the introduction and

spread of Islam as "the time of ignorance." Muhammad was born in the city of Mecca into the prominent Quraysh tribe. His life and ministry did

much to unify Arabia. Until the seventh century, the peninsula's tribes fought a destructive series of wars for control of the region. The situation

had changed dramatically by the time of Muhammad's death in A. D. 632. Muhammad, as well as his political successor Abu Bakr, enjoyed the

loyalty of almost all of Arabia. Although the Prophet did not appoint a spiritual successor, the institution of the caliphate emerged and expanded

the Islamic empire.

-Library of Congress

Based on the excerpt, in what way did Islam help unify Arabia?