Problems with the Use of the Zener Cards in Rhine's

Multiple Choice

Problems with the use of the Zener cards in Rhine's early experiments included all of the following EXCEPT

A) badly printed Zener cards that allowed the symbols to show faintly from the back.
B) subjects noting marks on the cards caused by normal use.
C) the experimenter unconsciously giving people cues.
D) the use of the double-blind experiments.