A scientist is trying to isolate a penicillin-resistant His- bacterial mutant from a mixed population. To isolate penicillin-resistant mutants, the scientist must inoculate the parent population on plates containing ; this approach is selection.

Which of the following statements best distinguishes a hypothesis from a theory? a. theories are hypotheses that have been proved. b.hypotheses are guesses; theories are correct answers c. hypotheses usually are relatively narrow in scope; theories have broad explanatory power. d. theories are proved to be true; hypotheses are often contradicted by experimental results.