A set of three glass bell jars was arranged as shown in the diagram. Bell jar P: a green plant was kept in sunlight for 8 hours. Bell jar Q: was left open to the air for 8 hours. Bell jar R: contained air breathed out by a student for 5 minutes. After the experiment, which bell jar contains the greatest amount of oxygen and which contains the smallest amount?
- Amost oxygen: P; least oxygen: Q
- Bmost oxygen: P; least oxygen: R
- Cmost oxygen: Q; least oxygen: P
- Dmost oxygen: R; least oxygen: P