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'.

Q: Question: What element plays a physiological role in the prevention of gastroesophageal reflux? 
 Options:  <1> Upper esophageal sphincter <2> Angle of His. <3> Hernia of Hiato. <4> Purkinje angle. <5> Pyloric sphincter

A: 2
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Q: Question: The oxygen of the ethers as that of the alcohols can be protonated to generate: 
 Options:  <1> Iminium ion. <2> Alkaloxonium ions. <3> Peroxides <4> Piranos. <5> Enaminas

A: 2
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Q: Question: We took a simple random sample of 1000 people, and for each one we checked whether or not he got the flu in 2012 and whether or not he got the flu in 2012. We obtained two responses for each of the 1000 people. To evaluate if there is an association between these two qualitative variables (having flu or not) and (having been vaccinated or not) from the data of our sample: 
 Options:  <1> We draw a quantile-quantile graph. <2> We perform a t test for the difference of means. <3> We calculate the Pearson correlation coefficient. <4> We make a contrast of the signs for the difference of medians. <5> We make a contingency table and an independence test.

A:
5
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