Detailed Instructions: In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
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: <0> Ventilation-perfusion ratio lower than normal. <1> Anemia. <2> Carbon monoxide poisoning. <3> Hypoventilation. <4> Shunt venoarterial.
A:
medicine