In Carl Sauer's theory, the is influenced by the site and the culture of the groups that occupy it.

According to Carl Sauer's theory, the term that describes the influence of both the site and the culture of the groups that occupy it is "cultural landscape." Sauer argued that the landscape is not just a physical environment, but also a product of human activity and cultural practices. He believed that human societies shape the landscape through their interactions with the natural environment, creating distinctive cultural landscapes that reflect their values, beliefs, and practices.

The term "sequent occupance" refers to the idea that landscapes are constantly changing as different groups occupy and modify them over time. While this concept is related to Sauer's theory, it does not specifically address the influence of both site and culture.

"Urban land" and "agricultural land" are more specific terms that describe different types of land use within a cultural landscape. They do not capture the broader concept of the influence of site and culture on the landscape as a whole.

Therefore, the correct answer is C. "Cultural landscape" best describes the concept in Carl Sauer's theory that the landscape is influenced by both the site and the culture of the groups that occupy it.