A radiograph shows a space between the post and the obturation material. What is the cause?

A space between the POST and GUTTA PERCHA on radiograph indicates that the POST SPACE was not properly prepared — the post space preparation did not match the post dimensions, or the canal walls were not correctly adapted. IMPROPER POST PREPARATION means the post space wasn't drilled to the correct size, length, or the walls weren't parallel, creating a void between post and GP. Insufficient obturation would be a separate issue seen on the initial post-op film. C is correct.