Answer: d. the amount of photosynthesis occurring exceeded the amount of cellular respiration.
Step-by-step explanation:
In the process of photosynthesis, oxygen is produced from carbon dioxide as plants make their own food. In cellular respiration, carbon dioxide is formed as oxygen is used to covert sugar into energy.
Photosynthesis produces oxygen and respiration produces carbon dioxide. If oxygen concentrations are increasing therefore, it means that more oxygen is being produced than being used which means that the amount of photosynthesis occurring must be higher than respiration because it is producing more oxygen than respiration can use.