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: Medicine
A raised serum creatinine phosphokinase level in unusual in - 
Select and explain. 
A. Acute alcoholic myopathy, B. Viral polymyositis, C. Myopathy of cushing's syndrome, D. Duchenne's muscular dystrophy
C: Myopathy of cushing's syndrome
Answer: C: Myopathy of cushing's syndrome 
Explanation: None