The double-blind experiment is one in which

The double-blind experiment is one in which
 
  a. the experimenters do not know which is the experimental group and which is the control group.
  b. the experimental subjects do not know that they are in the experimental group, and the control group subjects know that they are in the control group.
  c. neither the subjects in the experimental or control groups nor the experimenters know which are the experimental and control groups.
  d. the control group subjects do not know that they are in the control group, and the experimental group subjects know that they are in the experimental group.
  e. the experimental and control groups are given placebos.