20 points a population of mussels was observed in a particular ecosystem. it was found that crabs preferred these mussels as their favorite food. few mussels developed a thicker shell to protect themselves from crabs found in the region. which three statements does this adaptation suggest? a. a change in the environment led to a new distribution of traits in a population. b. the trait of shell thickening underwent natural selection. c. the trait for shell thickening will not be selected by future mussel generations. d. half of the mussel population developed the trait while the other half did not. e. mussels with the shell thickening trait had a greater chance of survival.