Researchers Using a Visual Cliff to Study Early Depth Perception

Researchers using a visual cliff to study early depth perception have found that infants:

A) at 2 months of age will show a change in heart rate when placed on the "deep" side of the cliff
B) show no response to the "deep" side of the cliff until they are 4 months old
C) who are 6 months old are willing to cross the deep side of the cliff
D) show no response to the "deep" side of the cliff until they are nearly 1 year old