Sequence of dna that is not involved in coding for a protein

Which of these statements are true about scientific theories and hypothesis

Which of the following is a limitation of a clinical trial? a.)amount of random assignments b.)hospital cost c.)number of test tubes d.)amount of peer review

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.