Review Question - QID 214617

A 21-year-old man presents to the emergency department with jaw pain. He says that the pain started 2 hours ago after yawning, and now he is unable to open and close his mouth properly. He has been studying for finals and has been especially tired the past 2 days. He has Ehler-Danlos syndrome and is currently not taking any medications. On exam, he has tenderness over the bilateral periauricular area with palpable indentation at the temporomandibular joint. His mouth is open and fixed with decreased active depression and elevation of his mandible. The physician places his thumbs intraorally on the inferior molars and applies inferior and posterior traction on the patient's mandible. Following this maneuver, the patient is able to perform the action shown in Figure A. Which of the following muscles is required to perform this action?