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: Streptococcus sobrinus and Streptococcus mutants are responsible for: 
 Options:  <1> Dental cavities. <2> Burns infections. <3> Rheumatic fever <4> Atypical rhinitis. <5> Otitis stockings.
[EX A]: 1

[EX Q]: Question: We want to study if Vitamin D can increase the incidence of breast cancer. In our area we have a population registry of cancer. To achieve our goal, all women diagnosed with breast cancer are selected from the register we have and each case pairs with two controls. What study design has been chosen? 
 Options:  <1> Prospective cohort study. <2> Cases and controls study. <3> Case-control study nested. <4> Retrospective cohort study. <5> Ecological study
[EX A]: 3

[EX Q]: Question: In the valuation of a strong base with a strong acid the pH of the equivalence point: 
 Options:  <1> It depends on the strong base that is valued. <2> It is determined by the excess OH ̄ of the solution. <3> It depends on the strong acid used as a titrant. <4> It is determined by the dissociation of water. <5> It is determined by the excess H + of the solution.
[EX A]:
4