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 specific procedure of the experimental strategy makes it the most appropriate to test hypotheses of causality? : 
 Options:  <1> The representative sampling of the participants. <2> The manipulation of the independent variable with control of possible strange variables. <3> The realization of the study in real contexts with natural groups. <4> The identification of possible predictor variables through the retrospective analysis of the study phenomenon. <5> The application of statistical techniques for the analysis of data.
[A]: 2


[Q]: Question: By what legal norm were regulated for the first time the specialties for the Diploma in Nursing and obtaining the title of Specialist Nurse? 
 Options:  <1> Order June 1, 1992 (BOE June 2). <2> Royal Decree 450/2005, of April 22 (BOE May 6). <3> Royal Decree 992/1987, of July 3 (BOE 1 of August). <4> Royal Decree 943/1986 (BOE May 14). <5> Order of July 15, 1980 (BOE of July 23).
[A]: 3


[Q]: Question: In gas chromatography, derivatization is very common, with several objectives. One of those discussed below is not among them: 
 Options:  <1> Increase the volatility of non-volatile compounds. <2> Avoid the decomposition of a compound, improving its stability. <3> Reduce the absorption on active surfaces of the walls of the column and the solid support. <4> Fragment the analyte in molecular ions of easier separation. <5> Improve the separation of closely related compounds with a very poor separation.
[A]:
4