Most medicines are made up of the active pharmaceutical ingredient (API) and various excipients. Which one of the following is NOT a possible

Most medicines are made up of the active pharmaceutical ingredient (API) and various excipients. Which one of the following is NOT a possible justification for formulating medicines in this way?

a) The excipients stabilise the API so that it does not degrade appreciably before administration

b) The excipients reduce the possibility of the API irritating the body

c) The API and the excipients each exert a pharmacological effect

d) The API is too potent to use undiluted