Why does the burning candle in bell jar A stops burning before the candle in bell jar B even when both bell jars are placed near a window in strong sunlight?
Oxygen gas is essential for burning. In bright sunlight, the potted plant in bell jar B produces oxygen by the process of photosynthesis. Thus, the level of oxygen in bell jar B is higher . and so, the candle burns for a longer time (because of the availability of more oxygen gas). On the other hand during the process of burning, oxygen gas is used up in jar A leading to its exhaustion. Thus, the candle is extinguished (due to lack of $O_{2}$).