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'.

Example Input: 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.
Example Output: 5

Example Input: Question: The excitotoxins activate: 
 Options:  <1> Nicotinic receptors <2> GABAA receptors <3> Glycine receptors. <4> NMDA receivers. <5> Na + channels dependent on voltage.
Example Output: 4

Example Input: Question: In a cohort study, the number of new cases of disease per person per unit of time is: 
 Options:  <1> The annual incidence. <2> The cumulative incidence or probability. <3> The prevalence rate <4> The density or incidence rate. <5> The relative risk of developing the disease.
Example Output:
4