As baby Sanjay’s physical development improves, he is able to crawl around and explore his environment. This advances his cognitive development, as he learns about the size and shape of objects, as well as how they function. His newfound crawling skills also contribute to changes in Sanjay’s psychosocial development. For example, he may experience anger when he picks up a breakable object, only to have one of his parents take it away. In addition, Sanjay experiences happiness when his parents encourage his motor efforts and frustration when they remove him from an unsafe area, such as the stairs. This example shows that the three areas of development .

A. confuse the infant
B. are independent
C. follow a single course
D. overlap and interact