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'.

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.
3

Question: Which of the following molecules has a simple covalent bond? 
 Options:  <1> C2. <2> N 2 <3> O 2 <4> O 3. <5> F 2
5

Question: In relation to the structure of proteins: 
 Options:  <1> All globular proteins have the same domains. <2> The tertiary structure is present only in oligomeric proteins. <3> Hemoglobin is the only protein that has a quaternary structure. <4> The protein domains are regions of compact folding that exert a certain function. <5> The tertiary and quaternary structures are maintained only by the peptide bonds.

4