C-shaped structure of alimentary canal is
a. Stomach
b. Duodenum
c. Oesophagus
d. Vermiform appendix

Hint: Alimentary canal is a muscular tube which starts from the mouth up to the anus. The various parts of the alimentary canal include mouth, teeth, oesophagus, pharynx, stomach, small intestine, large intestine and anus. Each part of the alimentary canal has particular shape and function.

Complete answer: The alimentary canal is a continuous passage which carries food through different parts of the digestive system and allows waste to exit the body. Small Intestine is the longest part of the alimentary canal and comprises three parts- Duodenum, Jejunum, and Ileum.
Duodenum- It is a C- shaped structure of the small intestine. Here, the pancreatic, bile and hepatic secretions are added to the food by hepato-pancreatic duct and chemical digestion takes place.
Jejunum- It is the middle part of the small intestine. It is a long coiled structure.
Ileum- It is a highly coiled structure that opens into the large intestine.



Among the given options:
Stomach is a muscular bag-like structure, positioned at the upper left part of the abdominal cavity. It has four parts- cardiac, fundus, body and pyloric.
Cardiac part- This part of the stomach is present close to the heart. The junction where the oesophagus opens into the stomach is regulated by the gastro-oesophageal or cardiac sphincter.
Fundus- It is a dome-shaped structure and is commonly filled with air.
Body- It is the main part of the stomach.
Pyloric- It is the posterior part of the stomach. It opens in the first part of the small intestine, duodenum. The opening of the stomach into the small intestine is controlled by the pyloric sphincter.
Oesophagus is a muscular tube like structure through which a small bolus of food passes from the mouth to the stomach with the help of peristaltic movements. The gastro-oesophageal sphincter regulates the movement of food into the stomach.
The vermiform appendix or appendix is a muscular narrow tube like structure attached to the cecum of the large intestine.

Note: Small intestine is so named as it has a small diameter. Its length is usually correlated with the height of the individual but not the weight. Among all the three parts of the small intestine, duodenum is the shortest and widest part. It is somewhat C-shaped.