Answer :
The correct answer is D. Life cycles.
Explanation
The life cycle is a term used to refer to the set of processes or stages in the life of living organisms on Earth that preserve the balance of ecosystems. In this, four fundamental processes are to be born, to grow, to reproduce and to die, at the same time all of these stages allow the renewal of organisms such as plants or animals, this can be explained as stages such as reproduction lead to new organisms being born, similarly as organisms die these are replaced by organism that have just started the life cycle. So, the correct answer is D. Life cycles.