The most accurate explanation for why religions expanded on trade routes is:
d. Merchants and traders exchanged ideas as well as products.
Trade routes served as conduits not only for goods but also for cultural exchange, including religious beliefs. As merchants traveled and interacted with diverse cultures, they shared their personal beliefs and religious practices, which often led to the spread of those religions among the societies they encountered. Additionally, the interconnectedness fostered by trade allowed for easier communication and the dissemination of religious ideas, promoting conversions and the establishment of religious communities along these routes.