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: Social & Preventive Medicine
Discrete variability are all except-a)  Color of skinb)  Boys in the class roomc)  Obesity weightd)  Leukocyte count 
Select and explain. 
A. ac, B. bc, C. ad, D. b
A: ac
Answer: A: ac 
Explanation: None