Final answer:
A face-to-face interview with the child is the best method for diagnosing depression in a 12-year-old, rather than using self-report inventories like the MMPI, which are intended for adults.
Step-by-step explanation:
The best diagnostic procedure to determine if a 12-year-old boy is depressed is D. Face-to-face interview with the child. While the Minnesota Multiphasic Personality Inventory (MMPI) is a valuable tool, it is primarily designed for adults and might not be suitable for children. The MMPI is a self-report inventory that includes a series of true/false questions to establish a clinical profile. However, for assessing depression in a 12-year-old, a face-to-face interview with a mental health professional is more appropriate for exploring the child's emotions and experiences in-depth.