Answer:
The correct answer is : decreases
Step-by-step explanation:
The development of the peppered moth is a transformative event of directional color change in the moth populace as a result of air contamination during the Industrial Revolution.
The melanic or dark color type of the peppered moth was not known before pollution level was low before 1811. Hence the decrease in pollution level in atmosphere will lowers the frequency of the melanic form of peppered moths.
Thus, the correct answer is : decreases.