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: Pharmacology
A newborn developed respiratory depression in a postoperative ward. It can result from the use of ? 
Select and explain. 
A. Opioid, B. Propofol, C. Furosemide, D. Heparin
A: Opioid
Answer: A: Opioid 
Explanation: None