The correct option is D Ileum
Digestion of proteins starts in stomach enzyme pepsin from gastric juice converts proteins into proteoses and peptones. The proteoses and peptones are acted upon by enzymes trypsin, chymotrypsin, and carboxypeptidase present in pancreatic juice in the small intestine and converted into the dipeptides. The small intestine secretes succus entericus which contains dipeptidase that converts dipeptides into amino acids in the ileum where they are finally absorbed.