单选题 Gilbert Roberts was shocked because ______.

A、 so many people had participated in the experiment
B、 so many of the participants were dishonest
C、 the effects of the pictures of flowers and gazing eyes were so different
D、 the effects of eyes and other perceptual signals were so powerful

【正确答案】 C

【答案解析】本题是细节题，从“The researchers found that staff paid 2.76 times more for their drinks when the image of the eyes was hung．‘Frankly we were shocked by the size of the effect,’said Gilbert Roberts，one of the researchers．”中可找出答案。