Two students are discussing how the adaptation of color in a population of beetles arose through evolution. This specific population consists almost entirely of brown beetles, which blend in well with their preferred habitat of fallen trees. Student A says that the reason that most of the beetles are brown is that the brown color of their habitat caused mutations in the beetles which made them brown, and brown is the best beetle color in this environment, because it makes the beetles harder for predators to
see.
Student B says that the beetle mutations were random,
and individual beetles who had a mutation that caused brown coloration were more likely to survive in the brown habitat because they are harder for predators to see, so they were the ones who survived, reproduced, and passed the genes for brown coloration to their offspring, resulting in a more brown beetles.

Which of the following best explains why the population of brown beetles grew more than the green beetles?
a. the green beetles' genes were not dominant, so they did not get passed onto as many offspring.
b. the brown beetles' offspring had more mutations, which made their genes express the brown color.
c. the green beetles produced more offspring with their traits than the environment could support.
d. the brown beetles were better able to survive to reproductive age and pass on their traits.