Choose the best explanation of the difference between evolution and natural selection.
A. Evolution is the idea that species change over time, and natural selection is a mechanism by which evolution takes place.
B. Natural selection is the idea that species change over time, and evolution is the idea that the species' food source also changes over time.
C. Evolution is the idea that species change over time, and natural selection is the idea that nature changes over time.
D. Natural selection is the idea that species change over time, and evolution is the idea that our world changes over time.