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: Pediatrics
Convulsions in a child with dehydration and vomiting can only be due to – 
Select and explain. 
A. Decreased serum sodium, B. Decreased serum magnesium, C. Decreased serum potassium, D. Decreased serum potassium
A: Decreased serum sodium
Answer: A: Decreased serum sodium 
Explanation: None