A certain species of insect is generally green in color, reports of brown insects of this species have been made. Scientists theorize that the color variation has occurred due to simple DNA mutation during DNA replication. This graph shows how the populations of green and brown insects have changed over time.

Which TWO conclusions would BEST support the scientists' theory?
A. New genetic combinations for color may have resulted during cross over.
B. A non-disjunction error could have led to the green color trait becoming less frequent.
C. The color mutation may be due to heritable mutations caused by environmental factors.
D. A lethal mutation may have caused the color change and rapid decline of green colored insects.
D. A substitution error in the more successful bugs could have resulted in brown color becoming more common trait.