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: Psychiatry
Two months after knowing that his son was suffering from leukemia, a 45 year old father presents with sleep deprivation, lethargy, headache and low mood. He interacts reasonably well with others, but he absented himself from work. The most probable diagnosis is : 
Select and explain. 
A. Depression, B. Psychogenic headache, C. Adjustment disorder, D. Somatization disorder
C: Adjustment disorder
Answer: C: Adjustment disorder 
Explanation: The information in this question is :

Stressor (knowledge about medical disorder in a child).
Mild depressive symptoms → low mood, sleep deprivation but normal social interaction Symptoms within 3 months of stressor.

The diagnosis is adjustment disorder.