Answer the following questions:
Arav records the following observations during different reactions:
| Reaction | Catalyst/Condition |
|---|---|
| I | Acidified \(K₂Cr₂O₇\) |
| II | Nickel catalyst |
| III | Sunlight |
| IV | Bromine water |
1. Which reaction involves the gain of oxygen?
2. Which statement is correct based on the table?
3. Arav's teacher asked him which sequence correctly arranges the reactions according to their type?