In a data engineering project, you are working with a DataFrame named 'df' that contains columns id, name, age, and gender. The project requires categorizing individuals into 'Minor' or 'Adult' based on their age, with 'Minor' being those under 18 and 'Adult' being 18 or older. The solution must use Spark SQL and specifically a CASE WHEN statement for this categorization. Additionally, the solution must be optimized for performance and readability. Considering these requirements, which of the following Spark SQL queries correctly implements the age_group categorization using a CASE WHEN statement? (Choose one correct option.)