Final answer:
The correct chest radiograph finding associated with pleural effusion is a concave interface border, which is also known as a meniscus sign.
Step-by-step explanation:
Among the given options for a chest radiograph observation most closely associated with pleural effusion, the correct answer would be C. concave interface border.
Pleural effusion, which is an abnormal accumulation of fluid in the pleural space of the lungs, is often identified on a radiograph by a concave upper border, also known as a meniscus sign, which is observed at the lung base when fluid settles due to gravity.
This is in contrast to the other patterns mentioned, which are associated with different lung conditions, such as the reticulogranular pattern typically seen in respiratory distress syndrome and a tree-in-winter pattern seen with bronchial diseases.