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
True about Schatzki\'s ring:.a) Has skeletal muscleb) Causes dysphagiac) Contains all the layers of the esophagusd) Located at lower esophagus 
Select and explain. 
A. c, B. bd, C. ab, D. ac
B: bd
Answer: B: bd 
Explanation: None