The prolonged increase in heart and breathing rates during the snow skiing trip was probably a result of: a. activation of the sympathetic autonomic nervous system by the new experience.
b. activation of the parasympathetic autonomic nervous system by the new experience.
c. hypoxia caused by insufficient blood hemoglobin concentration to supply oxygen for exercise at the low oxygen pressure found at high altitudes.
d. depressed core body temperature (hypothermia) caused by exposure to cold temperatures at high altitudes.

No they’ve not done that

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.