Final answer:
The first event was Muhammad traveling widely and establishing Islam. This laid the foundation for subsequent events: the conquest of the Sasanian Empire by Muslim armies, the spreading of Islam by Roman missionaries, and increased trade due to demand for goods.
Step-by-step explanation:
To arrange the following events in the order they occurred from the event that occurred first to the event that occurred last:
- Muhammad traveled widely there during this period. (a)
- Muslim armies conquered the Sasanian Empire. (b)
- Roman missionaries spread Islam to new regions. (c)
- Demand for goods meant more traders came to the region. (d)
The event that occurred first was when Muhammad traveled widely during this period. This was a critical time when the groundwork for the Islamic faith was being laid, as Muhammad united the Arabs in western Arabia and established Islam. Following Muhammad's travels and initiatives, the Muslim armies' expansionist desires, coupled with the recently united Arab tribes under the banner of Islam, led them to conquer the Sasanian Empire. Subsequent events, such as the spread of Islam to new regions by Roman missionaries, and more traders coming to the region due to demand for goods, followed as a result of the expansion and consolidation of the Islamic world.