a. trade connections gave Islam a presence in cities and ports where merchants went
Early on, Islam was spread peacefully through trade. At these trading centers, people not only exchanged goods, but also cultures and ideas. As merchants interacted and formed business relationships, different cultures learned to work together, and part of that was learning about each others' religion. Once a religion was discussed by many, it was typical that some form or all of it would be incorporated into other cultures as well.
