Final answer:
The rate of oxygen production is the dependable variable to measure for determining the rate of photosynthesis in an aquatic plant.
Step-by-step explanation
To determine the rate of photosynthesis in an aquatic plant, a suitable dependent variable to measure would be C) The rate of oxygen production. During the process of photosynthesis, aquatic plants utilize carbon dioxide and sunlight to produce glucose and oxygen. The oxygen produced is often released into the surrounding water, which can be measured using various methods such as the collection of oxygen bubbles or by using an oxygen probe. This measurement is a direct indicator of the plant's photosynthetic activity and is preferred over other factors like the color of the plant's leaves, the number of flowers, or the pH of surrounding water for assessing the photosynthesis rate.
Since photosynthesis is a process primarily driven by the availability of light and carbon dioxide, variations in these factors—as well as temperature and water availability—can have significant effects on the rate of photosynthesis. For example, increasing temperatures may enhance the diffusion rate of gases, leading to increased photosynthetic rates up to a certain point, beyond which it may start inhibiting the process due to factors like enzyme denaturation.