Final answer:
The people of Cahokia likely used solar observatories to know their ceremonial dates, which were special sites where they could observe celestial movements to keep track of time and date. The correct option is B. Solar observatories.
Step-by-step explanation:
The people of Cahokia were able to know their ceremonial dates through the use of solar observatories. Like many ancient cultures, the Cahokians observed the sky to keep track of time and date. They did not use stone markers, oral traditions, or written calendars in the same way as some other civilizations; instead, they had special sites to observe celestial movements.
Ancient observatories were used by various cultures to measure the positions of celestial objects, these observations were critical for regulating farming activities, scheduling religious ceremonies, and informing political decisions. For instance, in Chaco Canyon, buildings were aligned with specific celestial events, and the Sun Dagger marked solstices and equinoxes. Similarly, the Maya developed a sophisticated calendar that played a central role in rituals and may have influenced the scheduling of important events like battles.
As noted in archaeoastronomy, it's likely that Cahokia, with its sophisticated understanding of celestial events, used similar methods of sky observation at special sites to delineate ceremonial dates. These sites possibly functioned as ancient observatories, akin to famous structures like Stonehenge, which had specific alignments to the Sun and Moon during critical times of the year. While the exact methods used by the people of Cahokia remain a subject of study, we can infer that solar observations played a significant role in their calendar system.