In Which Situation Has a "Peak Shift" Phenomenon Occurred

Multiple Choice

In which situation has a "peak shift" phenomenon occurred?

A) Discrimination training using an orange S^D and yellow-orange S^Δ light produces maximal responding to a red stimulus.
B) Discrimination training results in a flat peak, with equal responding to the original training stimulus and several similar stimuli on either side of it.
C) Discrimination training using a loud tone and a bright light produces maximal responding to comparison tones and lights of moderate intensity.
D) Discrimination training produces two peaks in responding, one occurring at the S^D and the other at the S^Δ.