Eight-Month-Old Joey Has Learned to Crawl

Eight-month-old Joey has learned to crawl. Which of the following is most likely to happen when Joey crawls to the top of a flight of stairs?

A) Joey will not crawl over the edge of the first step.
B) Joey cannot perceive depth cues, so he is likely to crawl over the edge of the first step.
C) Joey has not yet learned to be frightened of drop-offs, so he is likely to crawl over the edge of the first step.
D) Joey will not crawl over the edge of the first step unless his mother coaxes him over.