whici of the following enzymes carries out the initial steps in the digaestion of milk in humans

Pepsin initiates the digestion process of milk. Renin is also present in humans.That is they are present in infants but as we grow into adults, this(renin) enzyme disappears gradually.So pepsin is the right answer. It cleaves the milk protein to a simpler form and initiates the digestion process.

In childhood secretion of renin in stomach help in digestion of milk but in adulthood chymotripsin help in digestion of milk because there is no secretion of renin.