Read the paragraph below.
Soon after the moving truck departed, I made way next door to greet the new neighbors. A boy was playing in the yard, and I greeted him and introduced myself. In response, the boy ducked his head and mumbled an inaudible reply. Though he smiled, he quickly retreated toward his mother on the porch. When I said, "Welcome to the neighborhood,” his cheeks turned pink, and he disappeared through the open front door.
What inference can be drawn about the boy?

He is upset by the narrator’s intrusion.
He creates imaginative games with others.
He prefers his friends from his old neighborhood.
He is shy and uncomfortable in new situations.