As we can see the image simulator has certain parameters that can be modified hence controlled, we have intensity (Watts), distance from the light source (cm), and filter, that is to say, frequency of light. Taking this into consideration we can analyze the available options:
Plant type: this is a parameter that we could control, nonetheless the option is not provided in the simulator so this cannot be.
Water amount: again is a parameter that could be controlled and is relevant for photosynthesis, nonetheless is not provided, so it cannot be either.
Environment: this parameter is not easy to control, however, under certain strict conditions can be done, but again this parameter is not provided so is not correct either.
Color of light: this parameter is provided in the simulator, as a filter. Light, as we can remember, comes in different wavelengths (each wavelength gives a color), so if we choose a filter, we are selecting different wavelengths, therefore this is the correct option.