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
In Duchenne's muscular dystrophy, which muscle is not involved -a) Gastrocnemiusb) Vastus medialisc) Brachioradialisd) Infraspinatus 
Select and explain. 
A. c, B. d, C. ab, D. bd
D: bd
Answer: D: bd 
Explanation: None