Why Do Researchers in the Area of Mental Imagery Need

Why do researchers in the area of mental imagery need to be concerned about demand characteristics?

A) Experimenters might unintentionally convey their hypotheses to the participants.
B) Experimenters typically expect participants to perform very well on imagery tasks.
C) When experimenters expect a certain outcome in their research, the participants unconsciously produce results that contradict this expectancy.
D) Demand characteristics typically increase the magnitude of individual differences.