Which tandem-seat turboprop trainer is used to train Navy and Marine Corps pilots?

The T-6 Texan is the correct choice as it serves as a tandem-seat turboprop trainer for Navy and Marine Corps pilots. It is designed to provide primary training for all U.S. military pilots, integrating various flight training programs into a single platform. The T-6 Texan features advanced avionics and a robust performance profile, making it an effective training tool for helping student pilots develop the skills necessary for advanced flight training and operations.

The other options, while significant in pilot training, serve different roles or are not used specifically for Navy and Marine Corps pilot training in a turboprop capacity. The T-34 Mentor is primarily used for earlier stages of training and is not the current primary trainer for these services. The T-45 Goshawk is a jet trainer also used by the Navy, but it is not a turboprop. The T-38 Talon, though a well-known jet trainer for the Air Force, does not align with the requirements of the Navy and Marine Corps training programs specifically focused on turboprop aircraft.