Suppose That Your Friend's Child Is Typical

Multiple Choice

Suppose that your friend's child is typical. If he asks you when he should expect that his child will learn to ascend and descend stairs, you should note that most children in the United States learn to crawl up stairs at about age ___ and learn to crawl down stairs at about age ___.

A) 11 months; 13 months
B) 13 months; 11 months
C) 12 months; 12 months
D) 14 months; 10 months