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: 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.

A: 2
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Q: Question: Among the epidemiological criteria of causality defined by Bradford Hill (1965) is NOT: 
 Options:  <1> Strength of association. <2> Temporal sequence. <3> Biological gradient <4> Cessation or reversibility effect. <5> Presence of alternative explanations.

A: 5
****
Q: Question: Which of the following enzyme complexes catalyzes the reduction of molecular oxygen to water during oxidative phosphorylation? 
 Options:  <1> ATP synthase. <2> Cytochrome c oxidase. <3> NADH-Q oxide-reductase. <4> Q-cytochrome c-oxide-reductase. <5> Succinate-Q reductase.

A:
2
****