<prompt> The marked structure on the X-ray is:NasopharynxEthmoidal air cellsSphenoid sinusPituitary gland  <response>: c Sphenoid sinusRef. Scott Brown, 6th ed., 432Shown below are X-ray Waters view occipitomental with open mouth and X-ray Nose PNS- lateral view. Note the highest sinus in the lateral view is the frontal sinus. 