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: Surgery
Parents bring their infant to the clinic, seeking treatment for vomiting and diarrhoea that has lasted for 2 days. On assessment, the nurse in charge detects dry mucous membranes and lethargy. What other findings suggest a fluid volume deficit? 
Select and explain. 
A. A sunken fontanel, B. Decreased pulse rate, C. Increased blood pressure, D. Low urine specific gravity
A: A sunken fontanel
Answer: A: A sunken fontanel 
Explanation: Option A: In an infant, signs of fluid volume deficit (dehydration) include sunken fontanels, increased pulse rate, and decreased blood pressure.
Options B  and C: These options are the opposite of the symptoms in a fluid volume deficit.
Option D: This is not a symptom of fluid volume deficit.