The answer is "Substage 3: Appearance of Secondary Circular Reactions".
The sensorimotor stage is the earliest in Piaget's theory of cognitive advancement. He depicted this period as a period of colossal development and change.
Secondary Circular Reactions (4-8 months): During this substage, the child turns out to be more centered around the world and starts to purposefully rehash an activity with a specific end goal to trigger a reaction in the earth. For instance, a kid will intentionally get a toy so as to place it in his or her mouth.