Scientists are looking to determine the primary productivity of a lake by analyzing its oxygen net primary productivity. How are scientists able to measure how much oxygen is used during a plant’s cellular respiration processes

When it is summer at the south pole, a. the northern hemisphere is tilted toward the sun. b. the southern hemisphere is tilted away from the sun. c. the northern hemisphere is tilted away from the sun. d. both the southern and northern hemispheres are tilted toward the sun.