In a new trial to test the effectiveness for a new type of medicine, why is it necessary for one group to receive a placebo?

Which of the following is an oxidation-reduction reaction? (pictured below)

Which best explains why there are 64 possible codons in the genetic code and only 20 amino acids that make protiens of living organisms on earth

Which best describes a gene? a. a sister chromatid b. a chromosome c. a tetrad d. a piece of a chromosome