Digestion of proteins is completed in smallintestine ,in duodenum.

The correct answer is ileum and duodenum
actually the digestion of proteins start in stomac
in stomach we can find an enzyme named pepsin which is produced at its inactive form pepsinogen and activated by gastric juice mainly hcl. the pepsin converts proteins in to proteises and peptones and again in duodenyn pancreatic juice is realased which converts proteises and peptons into dipeptises

Stages of protein digestion

Two stages are involved in the digestion of proteins: the first occurs in the stomach and the other in the in the duodenum, the first part of the small intestine.

The stomach and protein digestion

Protein digestion begins in the stomach, and this is a “preparation stage” compared to the events that occur in the duodenum.
The presence of food in the stomach stimulates G cells of the mucosa of the gastric antrum and proximal duodenum to produce and release the hormone gastrin into the bloodstream. The hormone stimulates the parietal cells of the proper gastric glands, localized mostly at the bottom of the organ, to produce and secrete hydrochloric acid into the stomach (parietal cells also produce the intrinsic factor, a protein that binds vitamin B

12

, preventing its destruction and allowing it to be absorbed).
In the proper gastric glands you also found:

mucous neck cells, that produce mucus;chief cells, that release pepsinogen.

All of these substances, together with others such as potassium ions and the gastric lipase, are present in the gastric juice, which has a pH that ranges between 1 and 2.5.
Due to its low pH, the gastric juice has an antiseptic action, killing most bacteria and other foreign cells, and a denaturing effect, as it breaks the noncovalent bonds that maintain the native structure of proteins. This denaturing effect facilitates the access of intestinal protease to peptide bonds, like the heating during cooking. Some proteinsrich in disulfide bonds, such as keratins, are resistant to denaturation by low pH, and hence difficult to digest. On the contrary, most of the globular proteins are almost completely hydrolyzed into constituent amino acids.
Finally, the low pH of the gastric juice activates pepsinogen, a zymogen, to pepsin, the first enzyme involved in protein digestion.