The letter that indicates the extent of Islam spread 100 years after Muhammad's death is C.
After the death of Muhammad in 632, Islam had a surprisingly rapid expansion for about a century, favored in the first instance by the weakness of the Byzantine Empire, and occupied all of North Africa, Iran, the southern part of Central Asia, the west of the Indian subcontinent, Spain and the south of France. This first stage concluded with several defeats, such as the Battle of Poitiers (732) and others against the Byzantines and Hindus, and with the dissolution of the Umayyad Caliphate.
