In the Classic Study on Mental Rotation, What Did Shepard

In the classic study on mental rotation, what did Shepard and Metzler find was the relationship between the speed that participants made judgments on whether two shapes were the same or different, and the degree of rotation?

A) the relationship between degree of rotation and response time was curvilinear
B) the greater the degree of rotation, the longer it took participants to respond
C) degree of rotation did not affect participants' response time
D) the greater the degree of rotation, the slower participants took to respond