Which of the Following Statements Describes Why Insulin Must Be

Which of the following statements describes why insulin must be injected?

A) Insulin is destroyed by gastric secretions.
B) Oral delivery results in a longer time for the peak effect to occur than does injection.
C) Continuous delivery by the transdermal route dose not conform to fluctuations in blood sugar levels.
D) Buccal administration is too fast to coincide with peak action.