Which one of the following accurately describes the lac operon? a. rna polymerase transcribes the lac genes when lactose isn't present. b. rna polymerase is prevented from transcribing the lac genes when lactose is present. c. the repressor protein binds to the operator when lactose is present. d. the repressor is freed from the operator when lactose is present

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.