Final answer:
Oxygen is being produced during photosynthesis in a water plant.
Step-by-step explanation:
The tiny bubbles forming on the leaves of a water plant during photosynthesis are actually oxygen bubbles. Therefore, the correct answer is b. oxygen. During photosynthesis, plants use carbon dioxide, water, and light energy to produce glucose and oxygen. The oxygen is released as a byproduct and can be observed as bubbles on the plant's leaves.