Which of the following radiological features, particularly on MRI, is highly characteristic and highly suggestive of an Aneurysmal Bone Cyst (ABC)?

Explanation:
An Aneurysmal Bone Cyst (ABC) is a highly vascular, locally aggressive, blood-filled cystic lesion. On MRI, the classic finding is multiple fluid-fluid levels within the loculations. This occurs because the red blood cells settle to the bottom of the cystic spaces, separating from the serum above when the patient lies still in the scanner. Reference: Miller's Review of Orthopaedics, 8th Edition.