Robin Hill discovered that the isolated chloroplasts from plants can release oxygen when they are illuminated by sunlight in the presence of a suitable electron acceptor. This showed:
| I. | oxygen \((O_2)\) is produced by a reaction that is separate from carbon dioxide \((CO_2)\) fixation. |
| II. | the reaction in which oxygen is released requires light. |
| III. | the light dependent reaction of photosynthesis is a result of a series of redox reactions. |
| 1. | I and II only |
| 2. | I and III only |
| 3. | II and III only |
| 4. | I, II and III |