Organisms that use the same resources because there may not be enough for all, so it then becomes a competition of who gets it and who doesn't.
Answer: D. Heat
Explanation : Water Vapor is a source of warmth, since the heat that is radiated from Earth is absorbed by the water vapor. This is why greenhouses use water vapor as well.
For you to understand the process we can say that the weak will die. If the animal or organism can't get food or find any it is naturally "selected" to die.So a Cuticle could have evolved like that. Hope tgis is useful