Final answer:
The spread of a language, like Spanish across different regions in the U.S., is an example of cultural diffusion. This process involves the adoption of cultural traits from one culture to another, leading to cultural convergence.
Step-by-step explanation:
The example of cultural diffusion among the options provided is A. the spread of a language, such as Spanish spreading across the U.S. Cultural diffusion refers to the spread of cultural elements, such as ideas, styles, religions, technologies, languages, and so on, from one culture to others. It happens through a variety of mechanisms including migration, trade, and the influence of media. When a culture adopts a trait from another, it is an example of cultural convergence where different cultures become similar to one another. Examples of cultural convergence extend to the worldwide popularity of US-based fast-food franchises, increasing use of the English language, adoption of new technology, and global sports.