This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of Gastrointestinal System Including Diarrhea, Subject name: Pediatrics
A 6-year-old drowsy child came in emergency with history of vomiting, loose motion for 3 days. On examination he had sunken eyes, hypothermia, skin on pinching was taking 5 seconds to reve. What is your diagnosis? 
Select and explain. 
A. No dehydration, B. Mild dehydration, C. Some dehydration, D. Severe dehydration
D: Severe dehydration
Answer: D: Severe dehydration 
Explanation: In this case, sunken eyes and skin "goes back very slowly" (in 5 seconds) in a "lethargic" (drowsy) child, so it is a case of severe dehydration.