Task: Question Answering
Input (English): Question: The eudismic index is a parameter with pharmacological interest that expresses the relationship between: 
 Options:  <1> Two diastereomer drugs. <2> Two bioisostero drugs. <3> Two enantiomers <4> A drug and a prodrug, structural analog. <5> Two structural modifications, one hydrophilic and one lipophilic, of a certain drug.
Output (English): 3