Answer:
similarity of the drug molecule to other molecules normally transported lung cells.
Step-by-step explanation:
As seen in the above question, to be most effective, this medicine must specifically enter the lung cell cytoplasm without entering the cells of other tissues. For this it is necessary that molecules responsible for bringing substances to the lung cell cytoplasms, take the drug there. For this to happen (and hence for the drug to be effective), there needs to be a similarity of the drug molecule to other molecules normally transported to lung cells.