F-5B.
The leading edge flaps are a dead give-away that it's an F-5. It's actually a slightly larger airframe than the T-38 as well. When I was in pilot training, I had T-38 instructor from the Spanish AF that had flown the F-5 for over 2,000 hours. He always talked about how much better the F-5 was compared to the T-38. Before I became I pilot I was a crew chief and my first fight chief crewed F-5s on active duty. He would get angry if you called it a T-38...
The T-38 was fast, sexy and an absolute blast to fly! Having said that, I would have much rather flown the F-5. The extra power, and slow speed handling (via the leading edge flaps) would have been mo better! There was something not quite right about flying the final turn at just the right amount of stall buffet!