Tell me the bone/osseous/spine situation based on the given paragraph by returning one of the letters (A/B/C/D), no extra texts. If bone/osseous/spine is not mentioned, return A; If bone/osseous/spine is abnormal, return B; If bone/osseous/spine is normal, return C; If it is not certain, return D. The paragraph starts: pa and lateral views of the chest were obtained.  since the prior exam, there has been no significant change.  the right pleural effusion with right basal atelectasis is essentially stable.  an air-fluid level in the right upper quadrant corresponds with a collection in the right hepatic lobe, better assessed on the prior ct scan.  the left lung remains clear.  no definite signs of new consolidation.  no pulmonary edema.  overall, cardiomediastinal silhouette appears stable.  bony structures are intact.