Act as if the world was a piece of paper rolled up where each end touched the other. then just pull them so they form a 2-D map.
An 18 month old baby and experiencing the world through senses is in Piaget's sensorimotor stage. The sensorimotor stage is the development of our senses such as, sense of sight, hearing, feeling, tasting and smelling. The sensorimotor stage is developed through 18 to 24 months of age.
Given the attitude of the grandfather portrayed in the problem, the most likely answer is
B) Go to the doctor regularly because he can monitor his health before problems get severe.
This would be because you are reminded, "prevention is the best medicine", and the answer B provides the precaution that is recommended.