The moth species biston betularia has two color morphs, or variants. one has a speckled white and black color, while the other is all black. in the early 1800s in england, the distribution was 10,000 speckled morphs to 1 black morph. that distribution changed dramatically between 1900 and 1950. by 1950, the distribution of the speckled morph had declined to less than 3% of the population and the black morph distribution increased to 97%. which statement most likely explains this change? a. a predator of the moth underwent steep decline, which reduced selective pressures on the moth. b. a chance mutation occurred in one black individual, which gave an advantage to the black morph's ability to survive. c. the changes are due to normal random fluctuations that might be observed in any population over time. d. changes in the environment changed each morph's ability to evade predation in different ways.