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
Best diagnostic modality for rotavirus diarrhea 
Select and explain. 
A. Isolation virus from stool culture, B. Detection of antigen in serum, C. Detection of antigen in stool, D. Detection of antibody in serum
B: Detection of antigen in serum
Answer: B: Detection of antigen in serum 
Explanation: None