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: A 13-year-old girl is operated on due to Hirschsprung illness at 3 months of age. Which of the following tumors is more likely to be present?
Options: <1> Abdominal neuroblastoma <2> Wilms tumor <3> Mesoblastic nephroma <4> Familial thyroid medullary carcinoma.
Example output: 2
Example explanation: The answer to the given question should be a tumor, therefore Wilms tumor is the correct answer for the given question.
Q: Question: When administering oxygen therapy to a patient admitted to the emergency room due to exacerbated COPD, you should take into account that:
Options: <1> The flow of oxygen must be high, since respiratory failure is accompanied by hypoxia. <2> The concentration of oxygen is conditioned by the patient's clinical situation. <3> The concentration of oxygen must be equal to the atmospheric concentration, since the patient presents hypercapnia. <4> The flow should be low, since hypoxia is the only stimulus to breathe. <5> The flow must be adjusted to achieve a PO2 greater than 90 mmHg.
A:
4