Final answer:
The palatine bones' horizontal plates form the posterior part of the hard palate.
Step-by-step explanation:
The posterior part of the hard palate is formed by the horizontal plates of the palatine bones. These are paired bones located at the back of the oral cavity, and together, they form the posterior quarter of the hard palate. The palatine bones are irregularly shaped and contribute to the walls of the nasal cavity and the medial wall of each orbit.
The right and left horizontal plates meet at the midline, and this junction completes the bony structure of the hard palate, which serves as the roof of the mouth and the floor of the nasal cavity.