In which of piaget's sensorimotor stages do infants respond to people and objects and seek to make interesting events last?

Stage 3

Explanation:

Sensorimotor stage is the time period between birth to 2 years. Jean Piaget expanded the sensorimotor stage into 6 stages:

Stage 1: Birth- 1 month: Exercise and organize reflexes like sucking, looking, grasping etc.Stage 2: 1-4 months: Adapt to the environment Stage 3: 4-8 months:  Repeat interesting events involving other objects or people to make them last.Stage 4 : 8-12 months: Goal directed behavior and development of new motor skillsStage 5: 12-18 months: Try to inculcate new behaviorStage 6: 18-24 months: Develop ability to solve problems