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'.

[EX Q]: Question: Which of the following conditions causes a decrease in the O2 saturation of the hemoglobin that is not due to a decrease in the partial pressure of oxygen? 
 Options:  <1> Ventilation-perfusion ratio lower than normal. <2> Anemia. <3> Carbon monoxide poisoning. <4> Hypoventilation. <5> Shunt venoarterial.
[EX A]: 3

[EX Q]: Question: Which of the following medications is an anti CD20 monoclonal antibody used in the treatment of rheumatoid arthritis? 
 Options:  <1> Alemtuzumab <2> Muromunab. <3> Abalizumab <4> Rituximab <5> Visilizumab.
[EX A]: 4

[EX Q]: Question: Ketogenic amino acids: 
 Options:  <1> They may contribute to the synthesis of glucose. <2> They are intermediaries of the urea cycle. <3> They are the substrate of reactions catalyzed by transketolase. <4> They can produce acetyl-coenzyme A. <5> They are eliminated in the form of ketoses.
[EX A]:
4