Which of the Following Is an Advantage of Double-Blind Studies

Which of the following is an advantage of double-blind studies?

A) They reduce the time to train coders to use the coding schemes, to collect behavioral data, and to prepare the coded data for analysis.
B) They allow researchers to unintentionally affect the outcome if they are aware of a study's hypotheses.
C) They prevent two potential problems with experimental designs, namely experimenter expectancy effects and demand characteristics.
D) They allow experimenters to give subtle cues to the participants as to how they should behave in the role of participant.