Final answer:
By 732, Islam had reached France marking the farthest point of expansion in the west.
Step-by-step explanation:
The letter that shows how far Islam had spread by 732, a century after Muhammad's death, is FRANCE. By the year 732, Muslim armies had already reached the heart of Europe, and their advance was halted at the Battle of Tours in France. This marked the farthest point of expansion for Islam in the west. Prior to that, Islam had spread to regions such as the Arabian Peninsula, Egypt, Syria, Mesopotamia, Persia, and even parts of India.
Learn more about Spread of Islam