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: Microbiology
SCID is due to deficiency of 
Select and explain. 
A. Adenosine deaminase deficiency, B. JAK 3 mutation, C. Recombinase - activating genes mutation, D. Any of the above
D: Any of the above
Answer: D: Any of the above 
Explanation: All of the above enzyme deficiencies cause SCID.
Mutation in cytokine receptors - M/c type defect.