Useful protein drugs, such as insulin, must still be administered by the cumbersome procedure of injection under the skin. If proteins are taken orally, they are digested and cannot reach their target cells. Certain no protein drugs, however, contain chemical bonds that are not broken down by the digestive system. They can, thus, betaken orally.

The statements above most strongly support a claim that a research procedure that successfully accomplishes which of the following would be beneficial to users of protein drugs?

• ACoating insulin with compounds that are broken down by target cells.but whose chemical bonds are resistant to digestion  
• BConverting into protein compounds, by procedures that work in the laboratory, the no protein drugs that resist digestion  
• CRemoving permanently from the digestive system any substances that digest proteins  
• DDetermining, in a systematic way, what enzymes and bacteria are present in the normal digestive system and whether they tend to be broken down within the body  
• EDetermining the amount of time each no protein drug takes to reach its target cells