Final answer:
The radiopaque area seen on maxillary molar radiographs at the lower distal portion is the maxillary tuberosity, a dense area posterior to the last molar.
Step-by-step explanation:
The radiopaque area seen on the lower distal portion of maxillary molar radiographs is the maxillary tuberosity. The maxillary tuberosity is a rounded area located on the distal end of the alveolar ridge, just posterior to the last molar. It is a site where connective tissue fibers attach and can appear as a radiopaque area on radiographs due to its density. The other options given, such as the zygomatic process, the coronoid process, and the hamulus, are different anatomical structures. The zygomatic process forms part of the zygomatic arch, while the coronoid process is an upward projection of the mandible for the attachment of muscles.