The most accurate statement about evolution from the provided options is:
Living things have adapted and changed over time for specific, discoverable reasons.
This reflects the understanding that evolution is a process driven by factors such as natural selection, mutation, genetic drift, and gene flow, leading to the adaptation of organisms to their environments over time. The other statements are incorrect or misleading. DNA is one piece of evidence among many that support evolution, scientists continue to study evolution as it's a dynamic field of research, and the concept that all living things share a common ancestry is foundational to evolutionary biology rather than being unrelated.