Final answer:
The Mayan calendar was used to predict agricultural seasons, which was critical for planning agricultural activities such as when to plant and harvest crops. It was not primarily used for warfare, financial transactions, or sold for profit.
Step-by-step explanation:
The Mayan civilization used their calendar to predict agricultural seasons. Understanding and anticipating the cyclical patterns of the seasons was crucial for early civilizations in planning when to sow and harvest crops. The Maya calendar was complex and consisted of various cycles including the solar year and the Calendar Round—a 52-year period. This system allowed them to track the passage of days and to count time into the distant past or future. Moreover, it was integral for identifying astronomical events and had significant importance in Maya rituals, religious ceremonies, and recording complex histories.
Although there are theories suggesting the Maya might have used their calendar to decide when to engage in battles—due to the noted alignment of historical battles with astronomical events—there is no direct evidence to support the claim that the calendar was primarily used for warfare strategies (option a). Likewise, there is no recorded evidence that the calendar was used for financial transactions (option b) or sold for profit (option c). Therefore, the most accurate way the Mayan calendar helped their civilization was by helping to predict agricultural seasons (option d).