If Antoine wants to learn more about how buyers behave, the most effective option from the list is "reading a book about marketing." Reading a book on marketing can provide insights into consumer behavior, market research, and effective strategies for understanding how buyers make decisions. This option offers a more in-depth analysis compared to the other activities listed.
While visiting a voting website, going to the movies, or studying photos in a newspaper could provide some contextual insights or trends, they are not specifically focused on buyer behavior like a comprehensive marketing book would be.