<prompt>  A radiograph of the mesial aspect of the mandibular right first molar show 2-3 mm of bone loss, yet clinical probing indicate a pocket depth of 6-8 mm. This discrepancy is probably due to the?Poor angulation used in taking the radiographPresence of mandibular tori in the areaPresence of mesial bone masking the destructionPresence of facial or lingual bone masking the destruction 