This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Which of these is an FDA approved indication for use of modafinil as an adjunct ? 
Select and explain. 
A. Major depression and associated lethargy, B. Narcolepsy, C. Obstructive sleep apnea, D. Shift work disorder
C: Obstructive sleep apnea
Answer: C: Obstructive sleep apnea 
Explanation: None