Final answer:
The light bottle/dark bottle method is primarily used to estimate net primary productivity by measuring the oxygen production due to photosynthesis and oxygen consumption due to respiration.
Step-by-step explanation:
The light bottle/dark bottle method is used to estimate net primary productivity, which is the rate at which photosynthetic primary producers incorporate energy from the sun. This method involves comparing the oxygen production in a light bottle, which allows both photosynthesis and respiration to occur, to the oxygen consumption in a dark bottle, which only allows respiration. By subtracting the oxygen consumed in the dark bottle from the oxygen produced in the light bottle, we can get an estimate of the net primary production due to photosynthesis. Thus, the correct answer to the student’s question is (d) photosynthesis and carbon budget.