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: The excitotoxins activate: 
 Options:  <1> Nicotinic receptors <2> GABAA receptors <3> Glycine receptors. <4> NMDA receivers. <5> Na + channels dependent on voltage.
[EX A]: 4

[EX Q]: Question: The set of means and systems that facilitate the contact of the infectious agent with the recipient subject corresponds to: 
 Options:  <1> Source of infection. <2> Habitat. <3> Transmission mechanism. <4> Biotope <5> Reservoir.
[EX A]: 3

[EX Q]: Question: Linear scanning polarography uses a working electrode of: 
 Options:  <1> Drops of mercury <2> Iodine drops <3> Platinum. <4> Calomelanos <5> Drops of cerium nitrate.
[EX A]:
1