Explanation

In Humans, starch is digested in buccopharyngeal cavity. Cellulose is not digested in the humans because cellulose contains$\beta - 1,\$4-linkage and vertebrates themselves do not possess any enzyme capable of hydrolyzing $\beta - 1,$ 4-linkages. Protein is digested in stomach and fat in small intestine. Thus, in the given options, fat and cellulose reach totally undigested in the stomach of humans.