Final answer:
The Spinosaurus had all the listed characteristics, including small nostrils centrally located on the skull, interlocking slanted teeth, and a flexible tail, indicating adaptation to an aquatic environment.
Step-by-step explanation:
The characteristics that the Spinosaurus, the first semi-aquatic dinosaur, had included: d. all of the above. Specifically, the individuals of this species showcased a. small nostrils located near the middle of the skull, b. slanted teeth that interlocked at the front of the snout that was particularly well-suited for catching fish, and c. loosely connected bones in the tail that likely aided in propelling the dinosaur through the water. The combination of these features suggests that Spinosaurus was well-adapted to an aquatic lifestyle.