Protein medicines, such as insulin, must still be implemented through a cumbersome subcutaneous injection procedure. If protein medicines are taken orally, they will be digested without reaching the target cells. However, some non-protein medicines contain chemical bonds that are not broken down by the digestive system. The above discussion most strongly supports the assertion that users of protein drugs will benefit if which of the following research objectives is successfully achieved. ['Permanently remove substances that digest protein in the digestive system.', 'Determine how long it takes for each non-protein drug to reach its target cell.', 'Encapsulating insulin is a mixture that can be broken down by target cells, but its chemical bonds will not be digested.', 'A systematic method to determine which enzymes and bacteria are present in the normal digestive system.']