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: A 19-year-old man consulted for a 24-hour history of pain, swelling and functional impotence of the right knee accompanied by a fever of 38C. Physical examination reveals inflammatory signs and joint effusion in the right knee. The analytical data show a leukocytosis with neutrophilia and an elevation of the C-reactive protein. The syndromic diagnosis of acute monoarthritis is made. What is the most likely etiologic diagnosis?
Options: <1> Arthritis by microcrystals. <2> Reactive arthritis <3> Bacterial infectious arthritis. <4> Infectious arthritis due to mycobacteria. <5> Rheumatoid arthritis.
Output:
3