The Following Question Refers to the Figure

Multiple Choice

The following question refers to the figure.
In an eight-year experiment, a population of E. coli, begun from a single cell, was grown in low-glucose conditions. The culture was transferred to fresh growth medium every 24 hours. Periodically, samples were removed from each population and the ability to survive in low-glucose conditions was compared with the original (ancestral) E. coli population.
The cells in the cell line grown in low-glucose conditions showed the effects of which of the following processes?

A) gene flow and genetic drift
B) natural selection and mutation
C) natural selection and gene flow
D) conjugation and transformation