The correct answer would be carcinogens. Carcinogens can disrupt cellular homeostasis and can even lead to uncontrolled cell division and form of cancers. These are substances that damages the cellular metabolic processes in the body. Carcinogens are found everywhere; it may be in our food, radiation or even some of the ingredients of the things we use daily.
D. Plants break down the glucose they produced in photosynthesis, and animals get energy from eating other organisms.
D because all the other answer are negative feedback
If another predator, that is more efficient hunter, enters the territory of the puffins, the puffins will find themselves in a very tough situation. They will either have to adapt very quickly, or die out.
The evolutionary pressure will be there fro the puffins to push them in a direction to adapt and be netter hunters, thus fight for their existence. That would mean that the puffin's beak, but also their speed and efficiency will have to improve in order to compete or even out-compete the new predator.
If the puffins do not manage to adapt relatively quickly, and a food shortage occurs, than they will die out, as they will lose the fight for food constantly.