Consider the activity and specificity of the three enzymes. pepsin is most active in the human and to digest a) mouth; starch b) mouth; protein c) stomach; protein d) small intestine; lipids

The correct answer is C) stomach; protein

Pepsin is an endo-peptidase i.e. it breaks down peptide bond and thus helps in breaking down proteins or larger polypeptide chains into smaller chains.  

It is secreted as pepsinogen (zymogen) by chief cells in the stomach. HCl (hydrochloric acid) released from parietal cells in the stomach converts pepsinogen into its active form pepsin.

It usually cleaves at the C-terminal side of amino acids such as tyrosine, phenylalanine, and tryptophan.

i would say it is