This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
Degree of freedom for 2/2 contingency table is? 
Select and explain. 
A. 1, B. Zero, C. 2, D. 4
A: 1
Answer: A: 1 
Explanation: Ref: Parks 23rd edition Degree of freedom = (r-1)(c-1) =(2-1)(2-1)= 1