Final answer:
Piaget would likely agree that a 5-month-old infant does not comprehend that the father still exists when he leaves the room, as it is around 8 months that infants reliably show object permanence.
Step-by-step explanation:
According to Jean Piaget's theories on cognitive development, a 5-month-old infant is in the sensorimotor stage, which lasts from birth to about 2 years old. During this period, a key conceptual milestone is the development of object permanence, which is the understanding that objects continue to exist even when they are no longer visible. However, it isn't until around 8 months that infants reliably demonstrate object permanence. Therefore, Piaget would most likely agree with the statement that at 5 months old, the infant fails to comprehend that his father still exists once out of sight (B).