What Does A Chest X-ray Showing A Central Trachea, Clear Lungs, Normal Hila And Diaphragm, Intact Ribs, And A Normal Cardio-thoracic Ratio Indicate?

Trachea is central. No focal active lung parenchymal lesion is seen. Both costo-phrenic angles are clear. Cardio thoracic ratio within normal limit. Both the hila are normal. Both domes of diaphragm are normal in shape and position. Visualised portion of ribs appear intact.