Answer:
B
Step-by-step explanation:
The correct answer would be during the daylight hours.
The production of oxygen in plants is dependent on photosynthesis, a process that requires the input of light in order to proceed.
This means that oxygen production would ordinarily cease in the absence of light (during nighttime hours) because photosynthesis would not take place and one would expect the greatest amount of oxygen to be produced during the day when photosynthesis is active.
The correct option is B.