Apatient presents with the sign of cystinuria. tests indicate that when a solution of free amino acids is infused intraduodenally, also, absorption of arginine is impaired; however, if a solution of dipeptides is infused intraduodenally, arginine absorption is almost normal. these data indicate that the patient has a deficiency in which of the following?
a. all sodium-coupled secondary active transport pathways in the intestinal epithelia
b. basic amino acid transporters in the intestinal epithelia
c. bile acid synthesis
d. epithelial cell peptidase activity
e. pancreatic enzyme secretion