Of the examples described below, which could NOT be used to test the idea that the feedback mechanism is in response to environmental conditions? A. Stomata on tobacco leaf opens in response to water and light signals B. A mountain climber starts to shiver, which warms him up. C. The arctic foxes have shorter extremities (tails, limbs, and ears) than the desert foxes to keep body heat retained more efficiently. D. Heart rate increases to provide more oxygen to the cells during an exercise.