Ageneticist conducts a study to investigate the prevalence of a certain genetic marker in a particular population of the united states (us) adult. during the study the geneticist observed the genetic code of 1,000 randomly selected us adults in the population and finds that 350 of those adults have the genetic marker. according to the results of the study, what is the ratio of observed adults with the genetic marker to observed adults without the genetic marker? a. 7: 13 b. 13: 7 c. 7: 20 d. 13: 20