This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Esophagus, Subject name: Surgery
MC site of Ca esophagus is: 
Select and explain. 
A. Middle 1/3 rd, B. Upper 1/3 rd, C. Lower 1/3 rd, D. Lower end of esophagus
A: Middle 1/3 rd
Answer: A: Middle 1/3 rd 
Explanation: MC site of Ca esophagus is middle 1/3 rd. Squamous cell usually affects the middle one-thirds;adenocarcinoma usually affects the lower third