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 type of epidemiological study indicated to evaluate, in a population initially exempt from the health problem under study, the association between a risk factor and the onset of the disease is: 
 Options:  <1> Randomized clinical trial. <2> Quasi experimental. <3> Ecological studies <4> Cases and controls study. <5> Cohort study.
[EX A]: 3

[EX Q]: Question: The water used in the preparation of medicated syrups must: 
 Options:  <1> Be sterile <2> Be purified or distilled water. <3> It is highly recommended that it contain dissolved carbon dioxide. <4> Contain dissolved calcium ions. <5> Contain an adequate proportion of magnesium ions.
[EX A]: 2

[EX Q]: Question: Legionella pneumophila is transmitted by: 
 Options:  <1> Air conditioning systems. <2> Contact between individuals. <3> Mosquito bite. <4> Contaminated food. <5> Fecal-oral route.
[EX A]:
1