What Is the Earliest Sign of a Left-Sided Pleural Effusion

Multiple Choice

What is the earliest sign of a left-sided pleural effusion on an upright chest radiograph?

A) An increased distance between the inferior margin of the left lung and the stomach gas bubble
B) Inability to see small pulmonary blood vessels over the left lower lung
C) A widened mediastinum
D) Elevation of the right hemidiaphragm