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
A 5-year old boy passed 18 loose stools in last 24 hours
and vomited twice in last 4 hours. He is irritable but drinking fluids. The optional therapy for this child is: 
Select and explain. 
A. Intravenous fluids, B. Oral rehydration therapy, C. Intravenous fluid initially for 4 hours followed by oral fluids, D. Plain water ad libitum
B: Oral rehydration therapy
Answer: B: Oral rehydration therapy 
Explanation: None