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: Radiology
Barium swallow is used for 
Select and explain. 
A. Esophagus, B. Colon, C. Duodenum, D. Jejunum
A: Esophagus
Answer: A: Esophagus 
Explanation: The esophagus is a muscular tube connecting the throat (pharynx) with the stomach.
The esophagus is about 8 inches long and is lined by moist pink tissue called mucosa.
The esophagus runs behind the windpipe (trachea) and heart, and in front of the spine.