Final answer:
d) Four seats. The Diamond DA-42 Twin Star fuselage has four seats, distinguishing it from the DA-40.
Step-by-step explanation:
The distinguishing feature of the Diamond DA-42 Twin Star fuselage when compared to the DA-40 is that it has four seats. The DA-42 Twin Star is designed as a twin-engine aircraft, and it can accommodate two pilots and two passengers. This is in contrast to the DA-40, which has a maximum capacity of four but typically has seating for only two pilots and one passenger. Having four seats allows the DA-42 Twin Star to carry more passengers, making it a suitable choice for flight training and small group trips.