You will be given a definition of a task first, then some input of the task.
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'.

Question: Hypoxemic hypoxia occurs when:
Options: <1> Oxygen diffusion of lungs is difficult. <2> There is decreased blood flow due to cardiogenic shock. <3> The decrease in hemoglobin due to anemia prevents its transport. <4> The cell membrane is altered and can not use oxygen. <5> None is correct.
Output:
1