Ingenhousz's experiments demonstrated that light plays a crucial role in the process of photosynthesis. In his work, he found that plants produce oxygen only in the presence of light. During daylight, plants take in carbon dioxide and release oxygen as a byproduct of photosynthesis, which occurs when light is available. Conversely, in the absence of light (such as during nighttime), plants do not produce oxygen; however, they continue to respire, which involves taking in oxygen and releasing carbon dioxide.
Thus, the correct response based on Ingenhousz's findings would be:
Light is needed for a plant to give off oxygen, but not to give off carbon dioxide.