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: Epidemiology allows early detection of changes in the incidence of a certain disease in the population. For this, the most correct thing is to use: 
 Options:  <1> The etiological investigation. <2> The description of the natural history of the disease. <3> Epidemiological surveillance. <4> The evaluation of the functioning of the services. <5> None of the previous answers is correct.

A: 3
****
Q: Question: Which of these foods should reduce a patient with high cholesterol from his diet? 
 Options:  <1> Cereals. <2> Vegetables. <3> Whole milk. <4> Olive oil. <5> Fish.

A: 3
****
Q: Question: The virus (virusoid) of hepatitis D (agent δ) needs to co-infect with the hepatitis virus: 
 Options:  <1> TO. <2> B. <3> C. <4> AND. <5> G.

A:
2
****