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: Anatomy
The esophagus - 
Select and explain. 
A. Begins at the upper border of cricoid cartilage, B. Runs a straight course throughout, C. Is narrowest at its termination, D. Is narrowest at its beginning
D: Is narrowest at its beginning
Answer: D: Is narrowest at its beginning 
Explanation: At the lower end of pharynx, at the level of lower border of cricoid cartilage, esophagus begins. It is narrowest at its beginning due to cricopharyngeal sphincter. Then it runs a curved route rather than being straight.