Small differences between parents and offspring accumulate over time. this process is what?

Small differences between parents and offspring accumulate over time and it is called evolution. This cannot happen within a short span of time, but over a long period of time. It can also be considered as a natural selection. For the survival of the offspring due to changes in environment or any other reason can be attributed to this fact.

Ihave no idea what the answer is

Answer accretion;