Which of the following organisms is most likely to survive?
a. the producers in a food web
b. the top carnivore in a food chain
c. a herbivore in a food chain
d. the top carnivore in a food web

The best answer here is A. the producers in a food web.

All the other answers  are dependent on the producers, but the producers are not dependent on others: if producers die, the others will die too, but not the other way: all the others can die off, and the producers can still survive.

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.

C) they are specialized meaning they are designed to do different things