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: Pulmonary hypertension occurs as a consequence of: 
 Options:  <1> Bronchoconstriction and inflammation of the upper respiratory tract. <2> Bronchoconstriction and inflammation of the lower respiratory tract. <3> Bronchiectasis and pulmonary collapse. <4> Vasoconstriction of the arterioles of the systemic circulation. <5> Vasoconstriction of the arterioles of the pulmonary circulation.
Example Output: 5

Example Input: Question: Sodium metal reacts violently with water because Na: 
 Options:  <1> Oxidize the water to oxygen, and the reaction is very exothermic. <2> It reduces the water to hydrogen, and the reaction is very exothermic. <3> Oxidizes the water to oxygen, and when a gas is generated, the entropy increases enormously. <4> It reduces the water to hydrogen, and the reaction is very endothermic. <5> It combines with water giving rise to an explosive hydride.
Example Output: 2

Example Input: Question: The binding of O2 to hemoglobin: 
 Options:  <1> Follow a hyperbolic kinetics. <2> It favors the transition from Fe2 + to Fe3 + in the heme group of the protein. <3> Induces the deprotonation of the protein. <4> It is facilitated in the presence of 2,3bisphosphoglycerate. <5> It is carried out through a covalent interaction with Fe3 +.
Example Output:
3