To infer about photosynthesis based on the information provided (with a focus on the light source's distance and its effects on gas production), the best choice would be:
a. The closer the light source, the higher the amount of oxygen gas produced.
This inference is based on the principle that photosynthesis requires light to produce glucose and oxygen. As the light source gets closer, the intensity of light increases, enhancing the rate of photosynthesis and consequently increasing the production of oxygen gas.