In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

[EX Q]: Question: Indinavir is a selective inhibitor of HIV protease because: 
 Options:  <1> By hydrolysis, the active drug is generated. <2> Rents irreversibly the active center of the enzyme. <3> Its structure mimics the transition state of the reaction catalyzed by the enzyme. <4> It is a suicide inhibitor. <5> Its symmetric structure interacts effectively with the active center of the enzyme.
[EX A]: 3

[EX Q]: Question: If I can not learn my new phone number because I always see the first three digits of the old one, what is the name of that type of interference? 
 Options:  <1> Proactive <2> Retroactive. <3> Coactive <4> Reactive <5> Protoactive
[EX A]: 1

[EX Q]: Question: Of the following reaction mechanisms, in which there is an inversion of the configuration from the reactant to the product of the reaction ?: 
 Options:  <1> Bimolecular nucleophilic substitution (SN2). <2> Unimolecular elimination (E1). <3> Unimolecular nucleophilic substitution (SN1). <4> Addition Markovnikov. <5> Addition anti-Markovnikov.
[EX A]:
1